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