Let
x---------> amount of money saved by Mark
x---------> amount of money saved by Neil
we know that
x=y+258-------> equation 1
x/y=(7/4)-------> equation 2
substitute equation 1 in equation 2
(y+258) /y=7/4--------> 4*(y+258)=7*y------> 4y+1032=7y
7y-4y=1032--------> 3y=1032------> y=$344
x=344+258------>x=$602
the answer is
$602