In a box there are red pens and black pens. The ratio of black pens to the total number of pens in the box is 3:5. If there are 120 red pens, how many black pens are there?

In what organelle does photosynthesis take place?

Evaluate the discriminant of each equation. tell how many solutions each equation has and whether the solutions are real or imaginary. x^2 - 4x - 5 = 0

Carl's candies has determined that a candy bar measuring 3 inches long has a z-score of +1 and a candy bar measuring 3.75 inches long has a z-score of +2. what is the standard deviation of the length of candy bars produced at carl's candies?