Răspuns:
a) 100 - 9a + 5 - 21 = 38
100 - 9a - 16 = 38
-9a + 100 - 16 = 38
-9a + 84 = 38
-9a = 38 - 84
-9a = -46
a = -46/-9
b) 8/4 + 9d - 27 = 39
2 + 9d - 27 = 39
9d - 25 = 39
9d = 39 + 25
9d = 64
d = 64/9
c)36 + 8a + 6 + 49 = 109
8a + 91 = 109
8a = 109 - 91
8a = 18
a = 18/8