What do you need? Two to five players (though more is fine), each with pencil and paper. Also five standard dice (easily simulated; try random.org or search the internet for "roll dice"), and a timer. 1- or 2-minute rounds are recommended, but preferences vary, and the game can work without any time pressure at all.
What's the goal? Get as close as you can to the target number, without going over.
What are the rules?
One player, the leader for the round, calls out a target number, anywhere from 33 to 99. Then the leader rolls the five dice and starts the timer. (Again, feel free to skip the time pressure if that's not your jam.)
Every player tries to achieve the target number by combining the five dice via the four operations of addition, subtraction, multiplication, and division. You must use each of the dice precisesly once, but you can pick and choose (and repeat) operations. Parentheses are allowed. Your final answer must be equal to or less than the target, and it must be a whole number, though fractions are permissible as middle steps.
When the timer goes off, compare your results. Your score is your distance from the target. (Thus lower scores are better.) To keep things civil, the maximum score for a round is 10.
Play until everyone has an equal number of turns calling the target. In the end, the person with the fewest points wins.
Rules and image from Math Games with Bad Drawings by Ben Orlin.