Question

A student expend 30% of his money and save rs 21rs find his amt

Answer 1

Let the amount he had be x
Therefore
$70\% = 21$
Therefore
$10\% = 3$
Thus
$100\% = 30$
Hence, he had 30Rs

Answer 2

Let his money be x.
Expend 30%of his money =x*30%=x*30/100
=3x/10
Save by him =x-3x/10=10x-3x/10 =7x/10
21=7x/10
21*10=7x
X=21*10 /7=₹30
His amount =₹30