How can we find HCF of a number

Solve for b. ab + c= d b= a + old ob=allc-ch b= (d-c/a

Sole the equation 6n + 9 = -3n - 21 - 6 for n

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