A pack of cards has one card missing. Two cards are drawn randomly...

${E}_{1}$ : Event denotes spade is missing

$P\left({E}_{1}\right) = \dfrac{1}{4}; P\left(\overset{¯}{E}1\right) = \dfrac{3}{4}$

$A$ : Event drawn two cards are spade

$P\left(\dfrac{A}{{E}_{1}}\right) = \left(\dfrac{C2 12}{C2 51}\right), P\left(A\overset{¯}{{E}_{1}}\right) = \left(\dfrac{C2 13}{C2 51}\right)$

$P\left(\dfrac{{E}_{1}}{A}\right) = \dfrac{\dfrac{3}{4} \times \left(\dfrac{C2 13}{C2 51}\right)}{\dfrac{1}{4} \times \left(\dfrac{C2 12}{C2 51}\right) + \dfrac{3}{4} \times \left(\dfrac{C2 13}{C2 51}\right)}$$= \dfrac{39}{50}$