Triangle ABC is similar to XYZ
Therefore, c times a scale factor is equal to z
Since c is 12 and z is 18, and we are trying to find the value of a, which is in the smaller figure, the scale factor from big to small is 12/18 or 6/9, Since I want to minimize x's value to get a, the scale factor must go from big to small, which is why the scale factor has to be 12/18 or 6/9. From there, to find a's value, i multiply 27 by 6/9 which is equal to 18. Therefore a=18
