Answer :
The fraction of his salary he does save is 3/10
What fraction of total salary is saved?
The fraction of the salary saved means the proportion of total salary that is neither spent on food nor on house rent, it can determined as the total salary minus the fractions spent on food and house rent respectively
If assume that the total salary is 1, when deducting 2/5 and 3/10 from 1 we can determine the part that is saved
savings=1-(2/5)-(3/10)
if lcm is 50, we would have the below
savings=(50-20-15)/50
savings=15/50
savings=3/10
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