If the theoretical yield of a reaction is 42.0 grams of product and the percent yield is 75%, how many grams were actually produced?

31.5 grams of product were actually produced.

The percent yield is the percent of the theoretical yield that was actually yielded in an experiment, so the answer would be 75% of 42.0 grams of product (31.5 g).

42.0 * 75% = 31.5

75% = 0.75 (in decimal form, used for calculations)