Can anybody help me know the Pythagorean theorem

Question 5 spring semester final exam math evaluate

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?

Find the solution of this system of equation -7x+y=-20 9x-3y=36