In \bigtriangleup ABC△ABC AB and BC are congruent. If the perimeter of \bigtriangleup ABC△ABC is 82 centimeters. How many centimeters long is AC?

AC = 2x

BC = 4x - 9
I don't understand it at all. Explain it to me please

make your sketch.

let AB = BC = y
let AC = x

so 2y + x = 82
x = 82-2y

given the information, that is as far as we can go