1:  2x(3-1)+4=12

For these expressions, we can go back to the PEMDAS for simplifying, then switching to then simply solving equations.

First, the parentheses can be simplified due to 3-1=2, giving us 2x(2)+4=12. Next, we can multiply 2x and 2, giving us 4x+4=12. 

After that, we can utilize the inverse operation of addition (subtraction) to subtract 4 from both sides of the equation, making the equation 4x=8. Finally, the  inverse operation of multiplication be used, dividing each side by 4, which gives us our final answer of x=2.

Answer: x=2

2: 3x+5x-2-1=19

In this equation, we have to combine a couple of like terms.

Firstly, 3x and 5x can be combined due to having the same variable and same exponent, giving us 8x-2-1=19. Secondly, we can combine -2 and -1 due to them both simply being regular numbers with no variables/exponents, making the equation 8x-3=19. 

Now that like terms are combined, it can be solved as usual, with first applying the inverse operation of subtraction and adding 3 to both sides, making the equation 8x=22. Finally, the inverse operation of multiplication can be utilized, dividing each side, giving us or final answer of x=2.75 or x=¹¹⁄₄.

Answer: x=2.75 or x=¹¹⁄₄

3: -8(3x-5x+3)=24

In this equation, we can already simplify before distributing, due to being able to combine the 3x and -5x to get -2x, making the equation -8(-2x+3)=23. 

Next, -8 can be distributed, multiplying with -2x to get 16x, and multiplying with 3 to get -24, making the equation 16x-24=24. Now, we can use the inverse operation of subtraction to then add 24 and get the equation 16x=48. Finally, the inverse operation of division can be used to get our answer of x=4.

Answer: x=4

4: 15x-3x+4(-1.5x+7)=35

Before looking at the equation, we should first distribute the 4 to both terms in the parentheses. Multiplying 4 and -1.5x will yield -6x, and multiplying 4 and 28 will give us 28, therefore making the equation 15x-3x-9x+28=35. 

We can now combine the like terms of 15x, -3x, and -9x, which combine to 3x, then making the equation 3x+28=35. The inverse operation of addition can be used, then subtracting 28 from both sides of the equation, giving us 3x=7. Finally, the inverse operation of multiplication can then be used, yielding the answer of x=2.5 or x=⁷⁄₃.

Answer: x=2.5 or x=⁷⁄₃

5: 9x+8-0.75(15x-11x+3)=24

In this equation, we can yet again look at the parentheses first, due to the 15x and -11x being like terms combining to get 4x. -0.75 then distributes to 4x yielding -3x, and distributes to 3 making the product -2.25. Now, we have the equation 9x+8-3x-2.25=24. 

The terms of 9x and -3x can be then combined to get 6x, and 8 and -2.25 to get 5.75, giving the equation 6x+5.75=24. The inverse operation of addition can then be used to subtract 5.75 from both sides to get 18.25, and the inverse operation of multiplication can finally be used, dividing both sides by 6, to get the answer of x=3.05.

x=3.04

6: -2.5(3x-9.5)+11x=-10.5

Firstly, we can distribute -2.5 to 3x as well as to -9.5. -2.5 and 3x can be multiplied to get -7.5x, and -2.5 and -9.5 to get 23.75. Now, we have the equation -7.5x+23.75+11x=-10.5. We can then combine -7.5x and 11x to get 3.5x, making our equation 3.5x+23.75=-10.5. 

The inverse operation of addition can then be used, therefore subtracting 23.75 from both sides to get 3.5x=-34.25. Finally, the inverse operation of multiplication can be utilized, dividing both sides by 3.5, and producing the answer of x=-9.79.

Answer: x=-9.79

1: 2x(8-3)-2x=24

2: 4(x-3)+x+14=40

3: 11x+9x+4(2-3x)=33

4: 7.8x+9(x-4.6)=45

5: -12(-0.5x-3)-19-4x=8

6: 29x-5-10.5(2x-0.65)=3

7:  -5x+4.5(x+4+2x)=-5

8: -9x+2(65x-81.1)-33x=698

9: 4x(9.7+9.3)-20.2x-31=48.25

10:  -8.5(4.6x-89)+9.0=201

11: 4.8(2x-9+93)÷5.25=528

12: 8[5x(3.8-2)+3.5x]-4x(13-5.5)+131=217

1: x=3

2: x=7.6

3: x=3.125

4: x=5.14

5: x=-4.5

6: x=0.15

7: x=-2.71

8: x=9.78

9: x=1.42

10: x=14.44

11: 246.75

12: x=1.23