(a) Which of the following has only one subset? (1) (i) {2} (ii) { } (iii) {Ǿ} (iv) None of these

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