Answer:
AC = 30 units
Explanation:
if AB = BC, then this is an isosceles triangle.
further BX intersects the base (AC) of the isosceles triangle at a right angle.
This means that the line of symmetry BX divides triangle ABC into two congruent triangles where AX = CX.
hence AC is
AX + CX
= CX + CX
= 15 + 15
= 30 units