Question

A pharmacist bought 4 boxes of mask. Each box contains 15 masks. He found that

10 masks were defective. How many masks are left with him?​

Answer 1

$mask \: \: in \: \: each \: \: box \: = 15 \\ = > masks \: \: in \: \: 4 \: \: boxes \: = 15 \times 4 \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = 60 \\ = > masks \: \: left \: \: = 60 - 10 \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = 50$