Answer:
B
Step-by-step explanation:
Let the nickels = x
Let the dimes = y
You don't know the total value of either. Nor do you know the total number of either.
You only know the total value of both together.
7.80 added to anything makes it bigger than 7.80 A is wrong.
y cannot be alone it should be multiplied by 0.5 C is wrong
D is wrong for the same reason A is
B is the correct answer. That is the way you write the problem
Number of Coins and value on one side. Total on the other.