Let N be the number of nickels in the jar, D the number of dimes and Q the number of quarters in the jar.
Recall that a nickel is 5 cents, a dime is 10 cents and a quarter is 25 cents. So, the expression
represents the total amount of cents we have, in nickels. In the same manner, we get the following expression for the dimes and the quarters
So, the total amount of cents we have in the jar would be the sum of these quantities. That is
This is one valid expression. However, we would like to write an equivalent one using the information we are given.
First, we are told that there are 8 times as many nickels as dimes. This means that if we take the number of dimes D and multiply it by 8, we get the number of nickels N. That is
Also, we are told that we have twice as many quarters as nickels. That is that if we multiply by 2 the number of nickels, we get the number of quarters. So we have
Replacing the value of N that we found before, we have
So now, we can replace all this values in our original expression. Thus, we end up with the expression