Answer:
$5,100
Explanation:
total amount of the loan: $13,600
part paid:

The question is how much of the $13,600 does the
that they already paid represent.
For this we need to multiply
by 13,600 :

we found that three eighths of $13,600 is equal to $5,100.
Thus they have paid off $5,100 of the loan.