What is the missing side length?

12

Step-by-step explanation:

5^2+12^2=13^2. It is a right triangle

look at the picture.

y-intercept for the function on a picture is 4 → point (0, 4).

y-intercept for the function

is for x = 0. substitute:

y-intercept is 8 → point (0, 8).