Is y = 3.4x + 5 proportional or non-proportional and why?

Answer 1

If y were proportional to x then if you double x, you double y
Try x = 1 and x = 2
y = 3.4 + 5 = 8.4
y = 6.8 + 5 = 11.8
I do not think that 11.8 is twice 8.4

Answer 2

However f they gave you
y = 3.4 x + 0
Then it might work
Try x = 1 and x = 2 and see if y doubles