What are the intercepts of the function

I'm terrible at math any here is appreciated.

You are on a cycling trip around europe with friends. you check the weather forecast for the first week. these are the temperatures for the week. sun mon tues wed thurs fri sat 16°c 20°c 24°c 28°c 28°c 23°c 15°c what is the mean temperature forecast for the week?

Write an equation for the function that includes the points (1,4/5) and (2,2/3)