To solve questions of these sorts, bring all the terms to one side & simplify it leaving x alone in the other side of the equation (other side of the equal to sign). After simplification you'll get the value of x.
Remember that the signs & operations will change when you bring a term to the other side of the equation.
So, addition will become subtraction, subtraction will become addition, multiplication will become division & division will become multiplication.
the dividing line would give the triangles the same length for one side, the side it divided, and then it says the triangles are congruent, meaning they are both the same triangle.