So, to figure out this problem you first need to solve for how much you have left after paying the base fee. Take the total ($84) and subtract by the base fee ($27). You will get 57 as your answer. Then, take $57 and divide it by $0.15 to get your answer. It is 380 minutes each month. The equation here is 84=27+0.15x.
Answer:
15. 2
16. 
or 1.6875
17. 
or 0.5666666667
18. 5
19. 
or 4.375
20. 
or 4.4
Step-by-step explanation:
Find common denominators. Multiply then simplify (if possible).
First let as solve all unit pirce
whistles 21.25 / 25 = $ 0.85 per unit
36 / 50 = $ 0.72 per unit
60 / 80 = $ 0.75 per unit
kazoos
10 / 25 = $ 0.4 per unit
18.50 / 50 = $ 0.37 per unit
27.20 / 80 = $ 0.34 per unit
a.) $ 0.85 - $ 0.72 = $ 0.13
b.) 10 / 25 = $ 0.4 per unit
c.) he must order 80 kazoos she should order
