Charlie's bag contains 4 blue pens and 3 red pens. He pulls out a pen at random, replaces it in the bag, and then pulls out a second pen at random. If the first pen is blue, what is the probability that the second pen is red

50 50 because there is 3 blue pens and 3 red plans after the 4th blue one was taken out
Mark brainliest

When rates are expressed as a quantity of 1, such as 2 feet per second or 5 miles per hour, they are called unit rates. if you have a multiple-unit rate such as 120 students for every 3 buses, and want to find the single-unit rate, write a ratio equal to the multiple-unit rate with 1 as the second term.