## Elementary Geometry for College Students (7th Edition)

(a) $AC = 12.3~cm$ (b) $x = 12.5$
(a) By symmetry, $AC = BD$. Therefore $AC = 12.3~cm$ (b) We can find the value of $x$: $AC = BD$ $3(x+7) = 9(x-6)$ $3x+21 = 9x-54$ $6x = 75$ $x = \frac{75}{6}$ $x = 12.5$