Expression of Fourth Angle

Question

The sum of the four angle measures of any convex quadrilateral is 360 degrees.

Suppose that a convex quadrilateral has angle measures of 90 , 2y+7 , and 10y-3 degrees.

Write an expression for the degree measure of the fourth angle.

Answer 1

Let's use the information we have, the sum of all the angles is 360 so an expression for the fourth angle would be equal to 360 minus the sum of the other three angles:

Fourth Angle = 360 - (90 + (2y + 7) + (10y -3))

Fourth Angle = 360 - (94 + 12y)

Fourth Angle = 266 - 12y