A standard deck of cards has 52 cards. Half of the deck has red cards and half has black cards. So the first probability would be 26/52, or 1/2 (simplified, it's half the deck).
Then you put the card back and choose a 3. There are 4 cards with the number 3 in the deck. So it's 4/52.
Then you multiply both the probabilities
26/52 x 4/52 = [tex] \frac{1}{2} x \frac{1}{13} [/tex] = 1/26
