Verified Answer :

AAmount of money earned by seji = s
    Amount of money earned by Gavin = g
   So, equation would be:  s+g = 425

B) Solving the system: s+g = 425
        we know, g = s+25
     Substitute it into the equation:
      s+s+25 = 425
      2s = 400
      s = 200
     so, g = 200+25 = 225

C) Graph for the equation, Mark (s,g) = (200,225) then, draw the line from the  origin.

D) Seiji earned = $200
    Gavin earned = $225   [ Solved in B part ]

Hope this helps!

For D

subtract $25 from $425 you will be left with $400 that is the total with out the addition $25 in which Gavin earned more of.

You are now left with $400 for both Gavin and Seiji
because they are 2 in number divide the money by 2 which will give you $200 each, then add Gavin's extra $25.

Gavin earned $225
and Seiji earned $200