By cross multiplication

(2 - 7x)(4 + 5x) = (3 + 7x)(1 - 5x)

⇒ 8 + 10x - 28x - 35x² = 3 - 15x + 7x - 35x²

⇒ - 35x² - 35x² - 18x + 8x = 3 - 8

⇒ - 10x = - 5