7/8 : (3/4x - 5/16) = 7/8
3/4x - 5/16 = 7/8 : 7/8 = 1
3/4x - 5/16 = 1
3/4x = 5/16 + 1 = 1 5/16
3/4x = 1 5/16
x = 1 5/16 : 3/4 = 21/16 : 3/4= 1 4/3
x = 1 4/3
ОДЗ
x > 17/3
lg (3x - 17)/(x + 1 ) = lg 1
(3x - 17)/(x + 1) = 1
3x - 17 = x + 1
3x - x = 17 + 1
2x = 18
x = 9
Ответ:
9
Получается Дима-9, Маша-6 , Зина -60 всего 75
(9, 86+2,1)*3,5-36,86=41,86-36,86=5