Final answer:
In the equation d = rt, solving for time t involves dividing both sides by the rate r, which results in t = d/r.
Step-by-step explanation:
If the equation is d = rt, which describes distance (d) equals rate (r) times time (t), to solve for time (t), you would divide both sides of the equation by the rate (r). This gives you the equation t = d/r. Substituting the correct variable for the question mark in the numerator and denominator, the answer is t = d/r. Option b, d/r, is the correct choice.