At heart we're being asked for a line through two points,

In general the line through (a,b) and (c,d) is

Check that you understand why both (a,b) and (c,d) are on this line.
Here our indepedent variable, instead of x, is T, temperature. Our dependent variable is v, velocity. Substituting,





That's our answer; let's check it.
When T=40, v = (5/9)40 + (2995/9) = 355 good
When T=49, v= (5/9)49 + (2995/9) = 360 good
Answer: wait I was wrong I saw thinking about something else
yes that is a unit rate.
Answer:
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The measure of the unknown angle should be 110 degrees. the measure of the angles have a sum of 180 degrees. the angles make up a 180 degree angle