a, $\frac{2x+1}{7}$ = $\frac{4x-1}{15}$
⇔ 15(2x+1) = 7(4x-1)
⇔ 30x +15 = 28x - 7
⇔ 30x -28x = -7 - 15
⇔ 2x = -22
⇔x = -11
b, $\frac{11x-2}{7x+5}$ = $\frac{11}{8}$
⇔ 8(11x-2) = 11(7x+5)
⇔ 88x - 16 = 77x + 55
⇔ 88x - 77x = 55 + 16
⇔ 11x = 71
⇔ x = $\frac{71}{11}$
c, $\frac{6x-5}{-7}$ = $\frac{5x-3}{-5}$
⇔ -5(6x-5) = -7(5x-3)
⇔ -30x + 25 = -35x + 21
⇔ -30x + 35x = 21 - 25
⇔ 5x = -4
⇔ x = $\frac{-4}{5}$
d, $\frac{2x+3}{-6}$ = $\frac{7x-3}{-15}$
⇔ -15(2x+3) = -6(7x-3)
⇔ -30x - 45 = -42x + 18
⇔ -30x + 42x = 18 + 45
⇔ 12x = 63
⇔ x = 21/4
⇔ x = 5,25
e, $\frac{2x+1}{3x+5}$ = $\frac{3}{7}$
⇔ 7(2x+1) = 3(3x+5)
⇔ 14x + 7 = 9x + 15
⇔ 14x - 9x = 15 -7
⇔ 5x = 8
⇔ x = $\frac{8}{5}$
