x(2x+3)-5(x2-3x)=3x(7-x)

2m+3m-m²-m=2m-m²+12

2m²-2m-12=0

Д= 4 - 4*2*(-12)=4+96=100=10²

x1=2+10/2*2=12/4=3

x2=2-10/2*2=-8/4=-2

x(2x + 3) - 5(x² - 3x) = 3x(7 - x)
2x² + 3x - 5x² + 15x =  -3x² + 21x
-3x² + 15x + 3x = 21x - 3x²
18x = 21x
x = 0
Ответ: x = 0.