Clara's Charity Run Speed Calculation

Clara is participating in a charity run to raise funds for local shelters. She plans to run a total of d miles. Every hour, she runs 3.5 miles.

After the first hour, she realized she needed to increase her pace to reach her goal. If she wants to complete the run in t hours total, how much faster (in miles per hour) does she need to run for the remaining time after the first hour?

Write an equation that represents the situation and solve for the speed needed for the remaining time.