Khan Academy
KhanAcademy.org is a great way to practice your math skills, so they won't get "rusty"! You can get to your school Khan account on your Chromebook:
log into your school Chrome account;
click this link: Khan Academy login
Click "Continue with Google". You won't need to put in any password, but you might need to click "Allow" to let Khan use your Chrome login for a month.
Good things to practice on Khan:
adding and subtracting fractions,
multiplying and dividing fractions,
long division,
division with decimals,
area of triangles,
area of parallelograms,
area of trapezoids,
volume and surface area of prisms.