Answer: A $50
The glasses cost 1200 dollars.
There are 12 months in a year.
Each month, Ralph is given his check two times, that means that Ralph receives his check 2(12), or 24, times per year.
Divide 1200 (the cost of the glasses) by 24 (the amount of times Ralph is given his check)
1200 / 24
Divide both numerator and denominator by 12
100 / 2
Simplify
50
Ralph should have put 50 dollars per pay check to pay for the glasses.