STEP 1:
find total price for keyboards
$83 per keyboard * 8 keyboards= $664 total for keyboards
STEP 2:
find total cost for monitors
Total cost - keyboard cost= monitor $
$872 - $664= $208 total monitor cost
STEP 3:
find price for each monitor
$208 ÷ 8 monitors= $26 per monitor
ANSWER: The price for each monitor is $26. The question says "which" is a reasonable estimate, so if there are choices listed, choose one close to $26.
Hope this helps! :)