Here are basic steps for using a protractor to measure an angle.

First, put the base line (marked with a 0 / 180) on one of the rays so that the other ray is covered by the protractor.

Also, put the center point of the protractor on the vertex of the angle as indicated by the blue arrow.

Next, you will read the protractor by starting on the ray on the base line as indicated by the red arrow.

Finally, by starting on the base line at 0 degrees and counting forward you will see the line passes through 50 degrees.

50 degrees is the measure of this acute angle.

Here are basic steps for using a protractor to measure obtuse angle.

First, put the base line (marked with a 0 / 180) on one of the rays so that the other ray is covered by the protractor.

Also, put the center point of the protractor on the vertex of the angle as indicated by the blue arrow.

Next, you will read the protractor by starting on the ray on the base line as indicated by the red arrow.

Finally, by starting on the base line at 0 degrees and counting forward you will see the line passes through 145 degrees.

145 degrees is the measure of this obtuse angle.