There are 21 nickels in carol bank
Solution:
Given that Carol's piggy bank consists of quarters and nickels
There are $ 4.55 in total
Let "n" be the number of nickels in bank
Let "q" be the number of quarters in bank
We know that,
1 quarter = $ 0.25
1 nickel = $ 0.05
Given that there are seven more nickels than quarters
Number of nickels = number of quarters + 7
n = q + 7 ---- eqn 1
From given question,
number of nickels in bank x value of 1 quarter + number of quarters in bank x value of 1 nickel = $ 4.55

Therefore from eqn 1
n = q + 7 = 14 + 7 = 21
n = 21
Thus there are 21 nickels in carol bank