Given parallel lines are 15x + 8y – 34 = 0 and 15x + 8y + 31 = 0.

Distance (d) between parallel lines Ax + By + C₁ = 0 and Ax + By + C₂ = 0 is given by

Here A = 15, B = 8, C₁ = -34, C₂ = 31

Distance between parallel lines is

∴ d = 65/17