Jackson buys a meal for his family for $18. The next day his friend pays him back the $5 that he borrowed last week. How has the amount of money Jackson has changed over the course of these two transactions?

Answer 1

Initially, Jackson has $0 because he borrowed $5 from his friend. Then he pays $18 for a meal for his family, leaving him with $0 - $18 = -$18.
Finally, his friend pays him back the $5 he borrowed, increasing his balance from -$18 to -$18 + $5 = -$13.
In total, the amount of money Jackson had has changed by $0 - $18 + $5 = -$13. Answer: \boxed{-\$13}.