Question

Can u please only answer b . i know the answer to a.

Answer 1

The weight of b boxes would be 60b.

In fact, a certain number of boxes will weight

`\underbrace{60+60+60+\ldots+60}_{\text{number of boxes}}`

This repeated sum of the same number is exactly what multiplication means and so if you sum 60 with itself b times, you'll end up with
`60* b`