First construct a table to look at the information of skaters vs temperature. Use skaters as the independent variable. Let S = Skaters and T = Temperature
Number of skaters Temperature
100 32
93 37
86 42
etc.
If you assume that this is a continuous relationship and has a constant slope, you can model using a line equation. Let's check the slopes.
Compare the first 2 points, the slope m = (100-93)/(32-37) = -7/5
Compare first and last points m = (100-86)/(32-42) = -7/5 OK! (As you would expect)
Then S-100 = -7/5(T-32) or S-100 = (-7/5)T + 224/5 or S = (-7/5)T + 224/5 + 500/5
So, S = (-7/5)T + 724/5