Respuesta :

if B is the mid point the two sides have to be equal

4x+3 = 3x+9

subtract 3x from each side

x+3 = 9

subtract 3 from each side

x=6

To find AC add 4x+3 and 3x+9

4x+3+3x+9

7x+12

7(6)+12

42+12

54

Choice D