Answer:
7. 2(x + 4) + 10 =2x+18
8. 3(6x) + 4 = 18x+4
9. 10(xy) = 10xy
10. 5(x + y) =5x+5y
11. 2(rs) + 4(x) = 2(rs+2x)
12. 2(q) + 2(x + t) = 2(q+x+t)
13. 6(7t + 4s) = 42t+24s
14. 9(10x) + 10y = 90x+10y
15. 2x(xy) =2x^2y
16. r(s)(t) =
17. (r)(s)(t)(x)(y) =
18. (7x + 2Y) =
I didn't know the last ones- sorry-