Farah has $700 in 20 dollar and 50 dollar bills. which of these could be the number of 50 dollar bills she has? a. 7 b. 8 c. 9 d. 11

I think c=9. I did the math...just trying to help but not exactly sure but I think it is...sorry

Option A:
Value of the $50 notes = 7 x $50 = $350
Amount left = $700 - $350 = $350
Number of $20 = . $350 ÷ 20 = 17.5 (Not a possible answer)

Option B:
Value of the $50 notes = 8 x $50 = $400
Amount left = $700 - $400 = $300
Number of $20 = . $300 ÷ 20 = 15 (Possible answer)

Option C:
Value of the $50 notes = 9 x $50 = $450
Amount left = $700 - $450 = $250
Number of $20 = . $250 ÷ 20 = 12.5 (Not a possible answer)

Option D:
Value of the $50 notes = 11 x $50 = $550
Amount left = $700 - $550 = $150
Number of $20 = . $150 ÷ 20 = 7.5 (Not a possible answer)

Answer B

The vertex of the quadratic function is (1.5, -.75)