Hi!
Let's write some equations to solve this.
s = Sofia
j = Jack
s + j = $520
j + $100 = s
Put the value of s into the first equation.
j + $100 + j = $520
Simplify
j + j + $100 = $520
2j + $100 = $520
Subtract $100 from both sides
2j + $100 - $100 = $520 - $100
2j = $420
Divide both sides by 2
2j/2 = $420/2
j = $210
Now that we know Jack has $210, let's find out how much Sofia has by putting that value into one of the equations.
$210 + $100 = s
Solve
$310 = s
Let's check our answer by putting the values into the first equation.
$310 + $210 = $520
This equation is true, so our answer is correct!!
The answer is Sofia saved $310
Hope this helps! :)
-Peredhel