A decimal problem may be a addition problem you would need to regroup the hundredths to solve, like a money problem
In the question, the angles proves that this triangle is an isoceles triangle.
So we can set the two sides equal:

Add

to both sides of the equation:

Divide both sides by 2:

We find that

. AC is also x, so, it is 6 too.
Each slice would cost 0.40¢.
This is because 2.40/6=.40