If a * b + 5 *a + 3 * b + 15= 24 and a+ 3 =6 then what is the value of a+b

a +b = 2

Step-by-step explanation:

a +3 = 6

    a = 6 -3

   a = 3

Plugin  a =3 in the equation,

a*b +5*a +3*b + 15 = 24

3b + 5*3 + 3b + 15 = 24

3b + 15  + 3b + 15 = 24      {combine like  terms}

3b + 3b + 15 + 15 = 24

             6b  + 30  = 24           {Subtract 30 from both sides}

                       6b = 24 -30

                      6b = -6               {divide both sides by 6}

                         b = -6/6

b = -1

a + b = 3 + ( -1)

         = 2

C

Step-by-step explanation: