$25 ... 1 month (installments for a TV screen)
$900 ... x months
If you would like to know how many months will she take to pay a total of $900, you can calculate this using the following steps:
25 x = 900 1 /25
x = 900 / 25
x = 36 months /12
x = 3 years
Result: 3 years equals to 36 months.
