Answer: $7
Step by step explanation: so first, we have to form any equation to show that some amount of money was added to eight dollars to get a total of fifteen dollars. Our equation becomes 8+x=15
Where eight is the origins amount, x is the amount that's added to the original amount and fifteen is the final amount.
We then move eight to the other side as a negative number
x=15-8
Therefore, x is equal to seven dollars.