In which central problem of an economy is the factor of 'scarcity' most evident?

A small scale soap business has the following expenses: 10% on marketing, 65% on employees salary and 25% on raw materials. If the business pays a total salary of Rs. 65,000 then what is its marketing expense?

There are $1500$ students in a school, $15\%$ are Muslims, $7\%$ are Sikhs, $8\%$ are Christians and remaining are Hindus. How many Hindu students are there in the school?

Current salary of Kriti is 4800. There will be increase of 15% in it in next year, what  will be the increased salary of Kriti after increment?

If $15\% of (x + y) = 45\% of (x - y)$, then $y$ is how much percent of $x$?