Răspuns:
Am schimbat X cu a
a) a x 9 = 18 x 4
9a = 72
a = 8
b) 5 x 27 = 15 x (10-a)
135 = 150 - 15a
15a = 150 - 135
15a = 15
a=1
c) 4 x 11a - 7 = 9 x 36
44a - 28 = 324
44a = 324 + 28
44a = 352
a=8
d) a-2 x 5 = 4 x a+3
5a - 10 = 4a +12
5a - 4a = 12 + 10
a= 22