3 Submit 1 point 154 A student on the track team runs 45 minutes each day as a part of her training. She begins her workout by running at a constant rate of 8 miles per hour for a minutes, then slows to a constant rate of 7.5 miles per hour for b minutes. Which equation describes the relationship between the distance she runs in miles, D. and her running speed, in miles per hour? a+b=45​