Final answer:
Benjamin has a total of 20 coins when he has 8 nickels and 12 quarters. If he has x nickels and y quarters, then the total number of coins is x + y.
Step-by-step explanation:
Benjamin finds a total of 8 nickels and 12 quarters under the couch cushions. To find out how many coins he has in total, we simply add the number of nickels to the number of quarters.
8 nickels + 12 quarters = 20 coins
Therefore, Benjamin has 20 coins in total.
If Benjamin has x nickels and y quarters, the total number of coins he has can be found using the same method of addition:
x nickels + y quarters = x + y coins
This equation represents the higher order addition of two variables, x and y, which stand for the number of nickels and quarters respectively.