First of all, we need the actual, final cost. 20% of 1200 is
[tex]\dfrac{1200\cdot 20}{100}=120\cdot 2=240[/tex]
So, if you add this extra to the initial cost, you have
[tex]1200+240=1440[/tex]
Subtract the initial deposity of 300, and you'll get what remains to be paid.
Divide this remainder by 10 and you'll get the monthly payment.
