Write an expression for 4th 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
,
6y+3
, and
8y-5
degrees. Write an expression for the degree measure of the fourth angle.

Answer 1

Since you know the four angles add to 360, write the sum. Call the unknown angle X.

X + 90 + (6y+3) + (8y-5) = 360

X = 360 - 90 - (6y+3) - (8y-5)

 

You can simplify from there by distributing the negatives and collecting like terms.

Answer 2

90, 6y³, and -8y⁵ are the three angles

the fourth angle is 360-90-6y³-(-8y⁵)=270-6y³+8y⁵