Answer:
B. x = 4
Explanation:
The two triangles have two congruent sides and a congruent angle. You can say ΔBAC ≅ ΔEDF because of SAS. Corresponding parts of congruent triangles are congruent, so you can say:
BC = EF
And we can substitute their values:
6x - 1 = 23
6x = 24
x = 4