b - 5/14b = 5 1/7
14/14b - 5/14b = 36/7
9/14b = 36/7
b = 36/7 : 9/14
b = 36/7 · 14/9
b = (4·2)/(1·1)
b = 8
- - - - - - - - - - - -
Можно привести обе части уравнения к общему знаменателю 14
14/14b - 5/14b = 5 2/14
9/14b = 72/14
9b = 72
b = 72 : 9
b = 8