Question

send me with procedure

Answer 1

$he \: spends \frac{2}{5} of \: his \: salary \: on \: food \\ remaining \: money = 1 - \frac{2}{5 } \\ = \frac{3}{5 } \\ he \: spends \frac{3}{10} of \: the \: remaining \: on \: house \: rent \\ = \frac{3}{10} of \frac{3}{5} \\ = \frac{9}{50}$
Sum of total expenditure is subtracted from 1
Then you will get answer.
I hope my answer help you.