Given:
Actual price of a violin is $1,250
Credit card monthly payment as $150.
Initial payment is $300.
[tex]\text{Total money paid by Ruben for violin=300+(150}\times9)[/tex][tex]\text{Total money paid by Ruben for violin=300+}1350[/tex][tex]\text{Total money paid by Ruben for violin= \$1650}[/tex]The difference between the total amount Ruben pays for the violin, including the initial payment and the credit card payments, and the sale price of the violin:
[tex]\text{Diffference amount=1650-1250}[/tex][tex]\text{Diffference amount= \$400}[/tex]Difference amount is $400.