Abuilding in a city has a rectangular base. the length of the base measures 75 ft less than three times the width. the perimeter of this base is 930 ft. what are the dimensions of the base?

By definition, the perimeter of a rectangle is given by:
 P = 2W + 2L
 Where,
 W: width
 L: length
 Substituting we have:
 930 = 2W + 2 (3W-75)
 Rewriting we have:
 930 = 2W + 6W - 150
 930 + 150 = 8W
 1080 = 8W
 Clearing W:
 W = 1080/8
 W = 135 feet
 The length will be:
 L = 3W-75 = 3 * (135) -75
 L = 330 feet
 
 the dimensions of the base are:
 W = 135 feet
 L = 330 feet