Move exactly 1 match to make this a valid equation.
In matchstick math puzzles, you are not allowed to make an inequality symbol such as ≠, ≥, >, <, or ≤. That would make it too easy!
Solution
Take the top right vertical match from the 9, and put it on top of the minus sign to make a plus sign:
15 + 13 = 28
15+13=28