Answer:
D. 8 * $5 + 10 * $1 = $50
Explanation:
You can solve the problem by writing equations, by trial and error, or by using each answer as a guess and seeing if it works.
Let's try the last method.
Each answer has a total of 18 bills, so we can't eliminate any answer on the basis of the total number of bills.
A. 10 * $5 + 8 * $1 = $58
B. 9 * $5 + 9 * $1 = $54
C. 7 * $5 + 11 * $1 = $46
D. 8 * $5 + 10 * $1 = $50
Answer: D. 8 * $5 + 10 * $1 = $50
If you specifically need to solve with equations, let me know, and I'll show that method to you.