Step-by-step explanation:
16. d-4 = -7
or, d = -7+4
or, d = -3
therefore, d = -3.
17. c-34 = 20
or, c = 20+34
or, c = 54
therefore, c = 54
18. a-4 = -18
or, a = -18 + 4
or, a = -14
therefore, a = -14
19. r-3 = 8
or, r = 8+3
or, r = 11
therefore, r = 11
20. z-100 = 100
or, z = 100+100
or, z = 200
therefore, z = 100
21. 5 = d - 1
or, 5+1 = d
or, 6 = d
or, d = 6
therefore, d = 6
