please show the work

Let's go little bit further.

x = ab therefore b = x/a ------------------(1)

y = 3b + a therefore b = (1/3)(y-1) ------(2)

From equation (1) and (2),

(1/3)(y-1) = x/a rearrange this equation gives

y = (3/a)x + 1

Therefore when x=0, y = 1 (Y intercept) and when y=0, x = -a/3 (X intercept)