Solve the proportion 4/5=28/x using two methods

Can someone me and plz do the problem

Randy and trey take turns cleaning offices on the weekends. it takes randy at most 4 hours to clean the offices. it takes trey at most 6 hours to clean the offices. what is the greatest amount of time it would take them to clean the offices together? 2.4 hours 2.5 hours

Multiply: 2.7 × (–3) × (–1.2). a. –9.72 b. –10.8 c. 10.8 d. 9.72