Răspuns:
a-5b=7 => a=7+5b
a) x+3a-15b=29
x+3(7+5b)-15b=29
x+21+15b-15b=29
x= 29-21
x= 8
b) x-123+5a-25b=137
x-123+5(7+5b)-25b= 137
x-123+35+25b-25b= 137
x= 137-35+123
x= 225
c) x-2a+10b+17=4
x-2(7+5b)+10b+17=4
x-14-10b+10b+17=4
x= 4+14-17
x= 1
d) 47-x+7a-35b=2a-10b+4
47-x+7(7+5b)-35b=2(7+5b)-10b+4
47-x+49+35b-35b= 14+10b-10b+4
-x= -47-49+14+4
-x= -78
x= 78
