We are going to say that D= Debt
So let's see the information we have.
Anthony borrowed 6.50, which can also be written as -6.50 because it is being taken away. The reason it's being taken away 8s because Anthony has $0 so if he borrows 6.50 that puts him in debt. he now has $-6.50
The same thing happens when Anthony borrowed $3.75 from his sister. here is the equation you can use to show how much debt he is in.
D=-6.50+(-3.75)
To complete the equation, you combine like terms.
D=-10.25
Anthony is $10.25 in debt.