1) 15c = 78-45+12
15c = 35
c=3
(6y+14) : 2 + 15 = 40
(6y+14) :2 = 25
6y + 14 = 50
6y = 36
y= 6
2) 16x + 5 = 133
16x = 128
x = 8
42k - 28k + 180 = 600
14k = 420
k = 30
3) 8y*5 = 56*5
8y = 280 : 5
8y = 56
y = 7
147a - 49 = (9+26) * 7
147a - 49 = 35*7
147a - 49 = 245
147a = 294
a = 2