a) 12+a+8+3a-3=49
4a+17=49
b) 4+3b+4b+5+4b-4+3b-5=49
14b=49
c) [(8+8+2c)*10]:2=120
(160+20c):2=120
80+10c=120
d) (2d*2*6):2=96
24d:2=96
12d=96
