Lets begin with the first sentence. We will let S = Sarah's monthly earnings and A = Andrews.
S = A + 525 (since Sarah earns more than Andrew).
Then you are told they spend 1250 each month and save the rest. The total savings will then be the difference times the number of months.
Savings per month (Sarah ) = S - 1250
Savings (Sarah Total) = (S - 1250)* number of months.
Plug in the number of months and total savings to figure out how much Sarah makes each month.
8250 = (S - 1250)*11
750 = S - 1250
S = 750 + 1250
S = 2000
From Sarah's earnings each month we can find Andrews (using the first equation).
2000 = A + 525
A = 2000 - 525
A = $1475
Finally you are asked for the yearly earnings:
12* $1475 = $17,700
Andrew earns $17,700 each year.
