Solve the formula S=4πr^2 for r

Afootball is throw by a quarterback to a receiver

David and alton are training for a race. they spend 35 minutes stretching and then go on a 5 mile practice run. david runs at a pace of 7 min/mile. alton runs at a pace of 8 min/mile. write an equation for each runner that shows the total length of their workout. then solve each equation showing your work

Each unit cost 14p, how much would 942 units cost?