(x+4/12)-4/15=16/35Помогите решить...

(х + 4/21) - 4/15 = 16/35

х + 4/21 = 16/35 + 4/15 = 48/105 + 28/105 = 76/105

х = 76/105 - 4/21 = 76/105 - 20/105 = 56/105

х = 56/105

Проверка: (56/105 + 20/105) -  28/105 = 76/105 - 28/105 = 48/105 = 16/35

Ответ: х = 56/105