How many parts are needed to prove triangles are congruent?

Two triangles are congruent if and only if they have the same three sides and the same three angles. That does not mean that the triangles are in the same position. If there is a turn or flip you can match these triangles to see that in fact they are congruent.

If the sides are the same, then the conclusion is that they are congruent, but this does not always work with angles, that is, two triangles with the same angles might be congruent or might not if they have different sizes because, even though all angles match, one side can be larger than the other.

The answer is: y would equal 3 because if you simplify the equation then it would be y= 3x+9 and if you divide 3x and 9 by 3 it would equal 3. y= 3