A bag contains 4 black, 5 white and 6 red balls. If 4 balls are drawn one by one with replacement the probability that none is red is 

A bag contains 4 black, 5 white and 6 red balls

$\mathrm{A}= \mathrm{event} \mathrm{of} \mathrm{not} \mathrm{getting} \mathrm{a} \mathrm{red} \mathrm{ball}\Rightarrow \mathrm{P}\left(\mathrm{A}\right)=\frac{9}{15}=\frac{3}{5}$

4 balls are drawn one by one with replacement

$\mathrm{probability} \mathrm{that} \mathrm{none} \mathrm{is} \mathrm{red} ={\left(\frac{3}{5}\right)}^4$