percent profit of 15 to 18

the profit is  18-15=3

3/15*100 percent

$${\frac{{\mathtt{18}}}{{\mathtt{15}}}} = {\frac{{\mathtt{6}}}{{\mathtt{5}}}} = {\mathtt{1.2}}$$ which means its $${\mathtt{0.2}}{\mathtt{\,\times\,}}{\mathtt{100}} = {\mathtt{20}}$$ 20% profit from 15 to 18.