Question

two angles form a straight angle. what is the one angle measures 89°. what is the measure of the other angle?

Answer 1

Sum of angles in a straight line is 180 degrees.
If the angles are two, it means they both add up to 180 degrees.

Since one of the angles is 89°, let the other be y.

y + 89 = 180

y = 180 - 89

y = 91

The other angle is 91° 

Answer 2

A straight line is = to 180 degrees (straight angle) so the formula would be
X+89=180
subtract the 89 from both sides and you get x=91
so the other angle is 91 degrees