A regulation girls fast pitch softball diamond has bases that are 60 feet apart. A regulation professional baseball diamond has bases that are 50% farther apart. Label the distance between the bases

The regulation bases are 50% further apart than the girls softball diamond bases. The girls softball diamond bases are 60ft, so if you take 50% of that (half of it), which is 30 feet, and add that to the 60, that becomes 90ft. There's your answer. Another way of looking at it is to say that 60ft is one whole, and that added 50% is a half. So, the regular diamond bases are 1.5 times further from each other. 60*1.5 = 90.