A vender bought 5 lemous for a rupee. How many lemons must be sold for ₹ 7 to gain `16(2)/(3)` ?

A vendor bought buttons at 6 for rupee.How many for a rupee must he sell to gain 20%?

If oranges are bought at the rate of 9 for a rupee, then how many oranges must be sold for a rupee so as to gain 12.5%?