Hi Logan
What we need to know is if $500.25 at least as much at 20% of $2,400.
The word "of" in the sentence above means multiply.
Convert the percentage to a decimal and multiply it by the amount of the installation.
20% is 0.20
0.20 x 2400 = $480
Since Sarah has $500.25, she has enough to pay the $480 down payment.