What is the answer to this math question

Which values for a and b will create infinitely many solutions for this system of equations? ax-y=8 2x+y=b

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. ?

Astudent showed the steps below while solving the inequality |x-4|< 1 by graphing.