Write the total distance equation 3B + 4*(B+15) = 410 miles total. where B is her average rate before lunch, in miles per hour. Simplify the equation and find B 3B + 4B + 60 = 410 7B = 410 - 60 7B = 350 B = 350/7 = 50. ANSWER. Terri's average rate before lunch was 50 miles per hour.