Find missing value to make a function….Thanks

Answer:
12
Step-by-step explanation:
First find the slope
m = ( y2-y1)/(x2-x1)
= ( 60-30)/(6-0)
= 30/6 = 5
Now using a second set of points and the slope we can find p (0,30) and (p,90)
5 = ( y2-y1)/(x2-x1)
5 = (90-30)/(p-0)
5 = 60/p
Multiply each side by p
5p = 60
Divide by 5
p =60/5
p = 12