Help? I give points also this work is due tomorrow and I really need help

What are “like terms”? why can we only add like terms?

If two angles of a triangle have equal measures and the third angle measures 90°, what are the angle measures of the triangle? a. 60°, 60°, 60° b. 45°, 90°, 90° c. 30°, 30°, 90° d. 45°, 45°, 90°

Why is causation so much more difficult to prove than correlation?