Use your knowledge about parentheses and substitution to solve the following:

7. 2(x + 4) + 10 =

8. 3(6x) + 4 =

9. 10(xy) =

10. 5(x + y) =

11. 2(rs) + 4(x)

12. 2(q) + 2(x + t) =

13. 6(7t + 4s) =

14. 9(10x) + 10y =

15. 2x(xy) =

16. r(s)(t) =

17. (r)(s)(t)(x)(y) =

18. (7x + 2Y) =