Let Salary/month be ‘X’, then
He spends 70% of his salary, as 40%, 20% and 10% on Food, Rent and Conveyance, respectively.
Rest of the 30% salary he saves. It is given that amount he saves is Rs 2000.
30 % of X = 2000
X = 6666.67
Salary/month = Rs 6666.67