1)5(x-3)+7=3(x+12);
5x-15+7=3x+36;
5x-8=3x+36;
5x-3x=36+8;
2x=44;
x=22;
2)5x+15+7=3x+36;
5x+22=3x+36;
5x-3x=36-22;
2x=14;
x=7;
3)5x+5*3+7=3x+3*12;
5x+15+7=3x+36;
Дальше как во втором;
4)2(a+2)-10=6(3-a);
2a+4-10=18-6a;
2a-6=18-6a;
2a+6a=18+6;
8a=24;
a=24/8;
a=3;
5)3(2y-1)+6(3y-4)=83+5(y-3);
6y-3+18y-24=83+5y-15;
24y-27=5y+68;
24y-5y=68+27;
19y=95;
y=95/19;
y=5