28 + (45 + х) = 100;
(у - 25) + 18 = 40;
(70 - х) - 35 = 12;
121 : (х - 45) = 11;
77 : (у + 10) = 7;
5y + 4y = 99;
54х - 27х = 81;
36y - 16y + 5y = 0;
14х + х - 9х + 2 = 56;
20y - 14у + 7у - 13 = 13.