Abcd is a quadrilateral. three of the angles of abcd measure 100°, 87°, and 106°, respectively. find the measure of the missing angle.

A quadrilateral is a polygon with four sides and four angles like a square, rectangle, diamond, or a trapezoid. A condition to be met for the angles of a quadrilateral is that the angles should sum up to 360 degrees. The four angles of a quadrilateral can be a combination of a right angle, acute angle, or an obtuse angle. Thus, for this problem, the missing angle is:

360°-100°-87°-106° = 67°

Think of it as five or above give it a shove. change the 5 or above to the right to a zero and add one to the number on the left.