#### Answer

$AC=DF = 19$

#### Work Step by Step

If two triangles are congruent, the corresponding angles and sides are congruent as well. Thus, we find:
$7a+5=5a+9\\
2a=4\\
a=2$
Plugging this back into the original equation, we obtain:
$AC=DF=2(5)+9 = 19$