Answer:
Step-by-step explanation:
Rob first borrows 15 dollars.
Later, he takes out another 3 dollars.
To represent this as an equation with ONLY negative integers, we write
-$15 + -$3 = -$18, which indicates Rob's debt.
If using numbers multiple times is allowed, the equation may also look like
-5 + -3 + -5 + -2 + -3 = -$18, which still represents his debt.
Thus, Rob owes his father $18, as shown by the negative sign "-"