8B Substituting positive numbers into algebraic expressions

To substitute means to replace each pronumeral in an expression with a number to obtain a final value.

For example, if we know that s = 5 we can evaluate or solve s + 7.

We substitute (or replace) the pronumeral with the number 5.

5 + 7 = 12.

Let's think back to Aurora's dog walking example.

Aurora is given $5 in pocket money for every time she takes her dog for a walk, we could write an equation for how much money she might earn.

Where P = total amount of pocket money and

 t = the amount of walks she takes we could write this as.

P = 5 x t

Now if Aurora walks the dog 6 times, we could substitute the number 6 for t.

P = 5 x 6

P = $30

And again with multiple pronumerals.