Simplify the following expression by combining like terms 7x + x + 9

What are “like terms”? why can we only add like terms?

It took alice 5 5/6 hours to drive to her grandparents' house for . on the way home, she ran into traffic and it took her 7 3/8 hours. how much longer did the return trip take? write your answer as a proper fraction or mixed number in simplest form. the trip home took __hours longer. ?

The roots of the function f(x) = x2 – 2x – 3 are shown. what is the missing number?