Angle Relationships

Complementary angles: Two angles that sum to 90°. Supplementary angles: Two angles that sum to 180°. Vertical angles: Formed by two intersecting lines. They are always equal. Linear pair: Two adjacent angles that form a straight line. They are supplementary (180°).

Example: Two angles are supplementary. One is 3x + 10 and the other is 2x + 20. Find x.

When you see intersecting lines, immediately mark vertical angles as equal and linear pairs as supplementary. This often gives you enough equations to solve for unknowns.