In this case, we are given the value of one angle and told to find the value of angle x. To do so, we will try to relate them based on the position they have in the diagram.
Notice that the two parallel lines split the space into two. One space is in between the lines, and the other space is outside the lines. We can see that both angles are located outside of the parallel lines.
Now, see that the third line splits the space into two. One space is on the left of the third line, and the other one is on the right of the third line. From the diagram, we can tell that each angle is on an opposite side of the third line.
This two relations between these angles (being outside the parallel lines and on opposite sides of third line) gives them the name of alternate outer angles. This angles have the property that they have the same measure.
So, we have the following
so the measure of x, in degrees, is 56°.