help please

$P[\text{first was blue | second was blue}] = \\ \dfrac{P[\text{second was blue | first was blue}]P[\text{first was blue}]}{P[\text{second was blue}]} = \\ \dfrac{\dfrac 1 5 \dfrac 1 3}{\dfrac 1 5 \dfrac 1 3 + \dfrac 1 3 \dfrac 2 3} = \dfrac{\dfrac{1}{15}}{\dfrac{13}{45} }= \dfrac {3}{13}$