The container has a total of 41 possible numbers from which to draw, and so each one as a probability of [tex]\dfrac1{41}[/tex] of being drawn.
Most of these numbers are even (21 of them) and
[tex]P(\text{even})=\dfrac{21}{41}[/tex]
20 of these numbers are greater than 30, so
[tex]P(\text{greater than 30})=\dfrac{20}{41}[/tex]
and among these, exactly half are even, so that
[tex]P(\text{greater than 30 AND even})=\dfrac{10}{41}[/tex]
So we have
[tex]P(\text{greater than 30}\mid\text{even})=\dfrac{P(\text{greater than 30 AND even})}{P(\text{even})}=\dfrac{\frac{10}{41}}{\frac{21}{41}}=\dfrac{10}{21}\approx0.48[/tex]
