Ab = 18.5, ax = 8.1 and bc = 18.5. what is the length of ac?

AC=16.2 units

Step-by-step explanation:

we know that

The triangle ABC is an isosceles triangle

so

AX=XC

because triangles ABX and CBX are congruents

AC=2*AX

see the attached figure to better understand the problem

therefore

AC=2*8.1=16.2 units

answer:   x = 3 + √11     and     x = 3 - √11

step-by-step explanation:

x² - 6x + 9 = 11

(x - 3)² = 11

x - 3 = ±√11

    x = 3 ± √11

x = 3 + √11     and     x = 3 - √11