First, you want to find the slope of the line. You do this by taking the difference in the heights divided by the difference of the time.
m=(20-12)/(5-3)
m=8/2
m=4
Now plug the information into slope intercept form (you can choose whichever set of data you want, just as long as you are consistent):
y=mx+b
12=(4)(3)+b
12=12+b
b=0
This is saying that there is no y-intercept (b).
So our final equation is:
y=4x
The question is asking for y when x is 1, so just plug it into the equation:
y=4(1)
y=4
Hope this helps!
