2.) what value for c will make the expression a perfect square trinomial?
x2 – 7x + c

-49/4
-7/2
7/2
49/4

The answer to your question is  a) C + J + S = 80

                                                     b) C = J + 5

                                                      c) S = 45 hours

Step-by-step explanation:

a) To represent the number of hours that they work together, just add the variables and equal them to 80.

            Carlito  +  Juan  +  Sara  = 80

               C + J + S = 80                                 Equation l

b) Juan worked 5 hours more than Carlito

              Juan = Carlito + 5

                  J = C  + 5                                     Equation ll

c) Hours worked by Sara

                  S = 3J                                          Equation lll

                  C = J - 5

Substitute equation ll and lll in equation l to find J

                J - 5 + J + 3J = 80

                5J = 80 - 5

                5J = 75

                  J = 75/5

                  J = 15

-Find S

                S = 3(15)

                S = 45 hours