Answer
a) ${\bf 7.7}\%$
b) ${\bf 25}\%$
Work Step by Step
$$\color{blue}{\bf [a]}$$
A regular deck of cards with 52 cards has 4 aces, so the probability of drawing an ace is given by
$$P_{\rm ace}=\dfrac{4}{52}\times 100\%=\color{red}{\bf 7.7}\%$$
$$\color{blue}{\bf [b]}$$
A regular deck of cards with 52 cards has 13 spades, so the probability of drawing a spade is given by
$$P_{\rm spade}=\dfrac{13}{52}\times 100\%=\color{red}{\bf 25}\%$$
