AI Tutor
When lines touch or cross, they create fixed geometric rules — which means if you know just one angle, you can find the mystery angle using a simple one-step equation.
An equation is a mathematical statement that two expressions are equal, where a letter like xx represents the unknown angle.

Complementary Angles

Two angles are complementary when their measures add up to exactly 90∘90^\circ, forming a square right angle.
To solve x+35∘=90∘x + 35^\circ = 90^\circ, we undo addition by subtracting 35∘35^\circ from both sides, revealing that x=55∘x = 55^\circ.
What happens if we unfold that right corner all the way out into a flat, straight line?

Supplementary Angles

Two angles are supplementary when they sit side-by-side along a straight line and sum to exactly 180∘180^\circ.
To find yy, we write y+125∘=180∘y + 125^\circ = 180^\circ and subtract 125∘125^\circ from 180∘180^\circ, giving y=55∘y = 55^\circ.
What happens when two straight lines cut completely across one another like an X?

Vertical Angles