John has 8 quarters, 3 dimes,and 7 nickels in the change holder in his car. He uses 16 of those coins, totaling $2.50, to buy some tacos. Which coins remain in the change holder?

8 Quarters + 3 Dimes + 7 Nickels = 21 coins

he uses 16 coins

21 - 16 = 5

he used 8 Quarters, 3 Dimes and 5 Nickels

therefore he has 2 Nickels left

but 8 Quarters, 3 Dimes and 5 Nickels = $2.55

Answer is A

18 coins to start and uses 16, 18-16=2

So 2 coins left over

8 quartes = 2.00

2 dimes = 0.20

6 nickels = 0.30

8+6+2=16 2.00+0.30+0.20 = 2.50

To solve this problem, we need to subtract the number and value of the coins John used to buy tacos from the total number and value of coins he had initially.

John initially had:
8 quarters = 8 * $0.25 = $2.00
3 dimes = 3 * $0.10 = $0.30
7 nickels = 7 * $0.05 = $0.35

The total value of his initial coins is $2.00 + $0.30 + $0.35 = $2.65

He used 16 coins worth $2.50 to buy tacos.

Now, let's find out which coins remain in the change holder:

Total value of coins he had initially - Total value of coins used to buy tacos = Value of remaining coins

$2.65 - $2.50 = $0.15

Now we need to determine the composition of the remaining coins based on their value.

In this case, the only possible combination of coins that equals $0.15 is:
1 dime ($0.10) + 1 nickel ($0.05) = $0.15

So, the correct answer is option a. 1 dime, 1 nickel.

To solve this problem, you could also list all the possible combinations and check which one adds up to $0.15. However, that would be time-consuming and more prone to errors, especially if there are more coins involved. By calculating the total value and subtracting the value of the coins used, we can quickly find the composition of the remaining coins.