Elevators starts 90 feet below ground level after 15s it is 20 feet below ground level. So the distance it has gone up is 70 feet because 90-20=70. Use this common equation: speed =distance/time and put your values in to get the correct answer. Time is 15s. You can eliminate c and d before you even start as the elevator is moving upwards. For the questions below just use a calculator.