since they're similair then similair sides will be proportional
CB is similair to EF
\frac{6}{8}86 = \frac{3}{4}43
same thing if you try with the hypotenuse AB similair to DE
\frac{13.5}{18}1813.5 = \frac{3}{4}43
So, if you multiply r (DF) by 3/4 you will get the similair side AC
rx 3/4=12
r= 12÷ 3/4
r=16.
i HOPE IT'S HELP
