I don’t know how to do 7 8 and 9. Can someone please help me

Matt and brian were solving a system of equations. they both noticed that the two lines had the same slope. brian said that because each line in the system had the same slope, the two lines had to be parallel, which meant the solution to the system was "no solution" matt disagreed, and said they should also look at the y-intercepts before determining how many solutions there were. who is correct?

The graph represents the gallons of water in a water tank with respect to the number of hours since it was completely filled

What is the greater volume 72 quarts or 23 gallons