Write the equation for the horizontal line going through the
point (3,7).
y =

 y = 7

This is because every point on this horizontal line has a y coordinate of 7.

For instance, the points (0,7) and (3,7) are on this horizontal line. The x coordinate doesn't matter. All that matters is that y is 7. Since x doesn't matter, it's the reason why it doesn't show up in the answer.

answer: option a.

step-by-step explanation:

you know that the quadrilateral opqr ( a four sided figure) is inscribed in circle. this means that all its vertices are on the circle.

then, by definition, the opposite angles of the quadrilateral are supplementary, this means that the sum of their measures is 180 degrees.

you can observe in the figure that the angles ∠opq   and the angle ∠orq   are opposite, therefore:

then, can be used to d to calculate the measure of ∠opq