When two angles add up to 180 degrees they are called

- First let's start with a Straight Angle:
**∠DEC**. We already know that Straight Angle are 180°. - Now let us draw a Ray
**EF**. The angle at**∠FEC**is 33°. - If we look at the diagram below, the two adjacent angles
are
**∠DEF**and**d∠FEC**. The sum of these two angles are 180° because they form a Straight Angle. - We know 180° minus
**∠FEC**equals**∠DEF**.**∠FEC**equals 33°. So 180° minus 33° equals 147°. So the angle at**∠DEF**equals 147°.

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