What is the greatest common factor (gcf) of 80 and 12?

Can someone me my sister? she is in third grade. 50 points and brainlist! ones that are not answered. plz and thx!

Answer this question! 30 points and brainliest! only if you know the answer.

James adds two numbers a + b. sally adds the same two numbers but reverse the order b + a what property of addition assures us that james and sally will get the same sum