The given equation is
x – 7y + 5 = 0
⇒ Ax + by + C = 0, where A = 1, B = – 7, C = 5
∴ The perpendicular line is
Bx – Ay + λ = 0
⇒ – 7x – y + λ = 0
⇒ 7x + y = λ
Since the line has x – intercept 3, so it passes through (3, 0)
⇒ 7.3 + 0 = λ ⇒ λ = 21
⇒ 7x + y – 21 = 0, is required equation of the line.
