What number is between 1 and 20 and has 5 factors?

What is the missing reason in step 5? linear pair postulategivendefinition of complementary anglescongruent complements theorem

If u good at math hit me up on insta or sum @basic_jaiden or @ and

Tom can paint the fence in 12 hours, but if he works together with a friend they can finish the job in 8 hours. how long would it take for his friend to paint this fence alone?