Ming-li spent $15 at the movies. she then earned $30 babysitting . she spent $12 at the bookstore. she now has $18 left . how much money did ming-li have to begin with?

How do i do this activity, is appreciated

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

A33.33 percent decrease followed by a 50% increase. greater or larger that original amount?