You need to equate the two expressions to get the value of x. That is 3x - 5 = x + 3 and solve for x, you will get x = 4. Then get the length of line ZB and line BA by substituting the value of x you've got; hence line ZB = 3(4) - 5 = 7 and line BA = 4 + 3 = 7. Add the two lines to form a single line ZA, that is 7 + 7 = 14. So the answer is D.14