Answer:
y = 42x
Explanation:
since it is linear it is proportional
using y = mx + c where m is the gradient
working out the gradient pick any two coordinates, I'll use (6, 252) and (12, 504)
m = 42
input m = 42 in y = mx + c
the equation is now y = 42x + c
use one of the coordinates (6, 252) or (12, 504), I'm using (6, 252)
y = 42x + c where y = 252 and x = 6, solving for c:
252 = (42 × 6) + c
252 = 252 + c
c = 0
so the final equation is y = 42x