Ineed more math , the! cement truck a can pour 200 cubic ft of concrete in 20 minutes. it only takes truck b 15 minutes to do the same job. if they both work together,how long will it take them to pour the 200 cubic feet? i need setting up the problem and solving it, you!

Track A takes 20 minutes
Track B takes 15 minutes
In 1 minute track be will do a fraction of 1/20, while track B will do 1/15
Both tracks in a minute = 1/20+1/15
                                      = 35/300
Therefore the two tracks will take 300/35 minutes to fill the 200 cubic feet
That is 300/35
           = 8.57  minutes
           ≈ 9 minutes

The answer would be c.(1,-3)

Hope it helps.