Answer:
x have to be equal to 3
Explanation:
Mathematically, when two triangles are similar, the ratios of their corresponding sides are equal
Thus, we have it that;
AB/AC = DE/DF
9/3(x-1) = 6/x + 1
9(x + 1) = 6(3(x-1))
9x + 9 = 18x - 18
18x-9x = 9 + 18
9x = 27
x = 27/9
x = 3