Alexa started a race with a 50 meter head start. she ran at a pace of 6.25 meters per second. after how many seconds was alexa 200 meters past the starting line?

Johnny rode his bike to a friends house 4 blocks down the street in his neighborhood. he immediately rode back home once he realized his friend was unable to play. what was his displacement for the total bike ride trip? what could you use as a reference point ? show the steps to solve this problem.