Mental Math Subtraction (Example)

In this video, Luca is at a store wanting to buy a video game costing $58. He has $139 and needs to calculate how much money he will have left after the purchase. To simplify the subtraction, the numbers are adjusted: 139 is increased to 140, and 58 is increased to 59. The subtraction is then performed in two steps: first subtracting 140 from 139, resulting in 90, and then subtracting 9, leaving Luca with $81. This method demonstrates an easier way to handle subtraction by adjusting numbers.

What new insight or understanding did you gain from this video?