- 4(2,3х - 4) - (3 - 2,6х) + 3(0,6х - 4) = - 9,2х + 16 - 3 + 2,6х + 1,8х - 12 = - 4,8х + 1
Если х = - 7/12, то - 4,8х + 1 = - 4,8 • (- 7/12) + 1 = 48/10 • 7/12 + 1 = (48 • 7)/(10 • 12) + 1 = (4 • 7)/(10 • 1) + 1 = (2 • 7)/(5 • 1) + 1 = 14/5 + 1 = 19/5 = 3 4/5 = 3,8.
Ответ: 3,8.