In triangle ABC it is known that AB = BC, angle ABC = 144 degrees. Find the angle of the BCA.

We introduce the unknown variable X
let the angle sav be equal to X degrees, so the angle sav is also equal to X degrees;
since in a triangle the sum of all angles is 180 degrees, it means that abc + sun + sav = 180;
taking into account that the angle abc = 144, and that sav = sun = X, it is possible to draw up an equation with one unknown: 144 + X + X = 180;
means 144 + 2X = 180;
find the value of X, for this we leave all the terms of equality with X on the left side, and transfer the rest to the right side: 2X = 180 – 144 = 36;
thus X = 36: 2 = 18.
Answer: the angle of the sun of this triangle is 18 degrees