The answer is B. This is because the triangle is an isosceles triangle, meaning that the answer to 4x-8 = x+4 You can rearrange this question to put the x’s on both sides and the integers on both sides so that 4x-x = 4 + 8. This cancels down to 3x = 12. To find x, divide 12 by 3, which is 4. To check this answer, you can input 4 into both of the equations. (4 x 4) - 8 = 8, and 4 + 4 is also 8. Hence, you know x = 4.
Another, more time-consuming way of doing this question would be to simply input each possible value (A, B, C and D) into both equations until the both equations came out with the same number. Hope this helped :)