x + x/12 = 13/2
12x + x = 6 * 13
13x = 13 * 6
x = 6
2) 2(х+21)+3(х-4)=5(х+6)
2х+42+3х+12=5х-30
2х+3х-5х=-30-42-12
x =-84
3) 5(3х+4)-6(3х-7)=23х
15х-20-18х+42=23х
15х-18х-23х=20-42
−56х=−22+56
х=34
George Washington was the first American president.
I hope this helps you
15 секунд т. к. на каждый час на три секуны больше
4у+9=-8+5у
4у-5у=-8-9
-1у=-17
у=17
Ответ:17