Question:
Two angles of a quadrilateral measure 85° and 75° respectively. The other two angles are equal. Find the measure of each of these equal angles.
Solution:
Let the two unknown angles measure $x^{\circ}$ each.
Sum of the angles of a quadrilateral is $360^{\circ}$.
$\therefore 85+75+x+x=360$
$160+2 x=360$
$2 x=360-160=200$
$x=100$
Each of the equal angle measures $100^{\circ}$.