At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident, similique sunt in culpa qui officia deserunt mollitia animi, id est laborum et dolorum fuga. Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus, omnis voluptas assumenda est, omnis dolor repellendus. Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat.
Here is the figure. |dw:1436386396920:dw|
The lines in bold black are lines and form angles x and y. |dw:1436386494600:dw|
What is the sum of the measures of angles 1, 2, 3, and 4. When a bunch of angles add up to a straight angle, what do their measures add up to? |dw:1436386563967:dw|
Are you familiar with a straight angle?
Ok. Here is a refresher for your memory.
Opposite rays are rays that lie on the same line, have the same endpoint, but they go in different directions. Here is line m. |dw:1436386851147:dw|
Here are points A, O, and B, on line m. |dw:1436386879204:dw|
Now look at rays OA and OB. They are opposite rays because they lie on the same line, have the same endpoint, and go in different directions.
The angle formed by rays OA and OB is angle AOB. Angle AOB is a straight angle and its measure is 180 degrees.
A straight angle is an angle formed by opposite rays. The measure of a straight angle is 180 degrees.
Do you remember straight angles better now?
The angles measuring x, 80 and 60 form a straight angle, so their measures add up to 180 deg. |dw:1436387213264:dw|
Now you can write an equation that can be solved for x.