Ok the first thing I recommend you doing is making a formula. [tex]m+g=t[/tex]
Next you should plug in the numbers. [tex]825+200=t[/tex] [tex]=1025[/tex]
Then you will have another formula. [tex]p-t=n[/tex]
p=1250
so.... [tex]1250-1025= n[/tex]
n=how much is needed.
He need's $125 to complete the money needed to buy his computer
Hope I helped. :)