-------------------------
-------------------------
-------------------------
7у+у+27=99
8y+27=99
8y=99-27
8y=72
y=72 / 8
y=9
-------------------------
42х-28х+180=600
14x+180=600
14x=600-180
14x=420
x=420 / 14
x=30
-------------------------
15х-х-16=82
14x-16=82
14x=82+16
14x=98
x=98/ 14
x=7
-------------------------
8х+14=870
8x=870-14
8x=856
x=856 / 8
x=107