What is the probability of rolling a number greater than or equal to 8 with the sum of two dice given that at least one of the dice must shown as a 6?

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.