8. Powers and letters a^2 * a^3
7. Working out brackets 5(a + c)
9. Subtracting terms with brackets 8y - 2x(y+7) 
7. Working out brackets 5(a + c)
9. Subtracting terms with brackets 8y - 2x(y+7)
Exercises
Unfortunately, at the moment there are no exercises available.
It is planned as a future functionality.