17. True (bc anything multiplied by 0 equals 0)
18. True (bc 13=13)
19. True (bc 6=6)
20. True (bc 7(x-3)=7x-21)
21. True (bc the negative sign cancels out the positive sign)
22. True (bc y=3 and 3=y are the same)
23. True (bc they are the same just rearranged)
24. True (because x and z both equal -1)
25. True (anything multiplied by 1 stays the same)