x+8/5x+7 = x+8/7x+5
(7x + 5) * (x + 8) = (5x + 7) * (x + 8)
7x² + 56x + 5x + 40 = 5x² + 40x + 7x + 56
7x² + 61x + 40 = 5x² + 47x + 56
2x² + 14x - 16 = 0
x² + 7x - 8 = 0
D= 7² - 4*(-8) = 49 + 32 = √81 = 9
x₁ = (-7+9)/2 = 2/2 = 1
x₂ = (-7 - 9)/2 = -16/2= -8
ответ: -8 ; 1