To find out how much Mrs. Perez should write the check for, you need to subtract the amount she paid in cash from the total price of the refrigerator.
Total price of the refrigerator: $1368.25
Amount paid in cash: $497.80
Now, you can subtract:
$1368.25 - $497.80 = $870.45
Therefore, Mrs. Perez should write the check for $870.45.