What are some examples of mathematical concepts which are very intuitive but difficult to prove mathematically? No answer needed!

Two angles are complementary. the larger angle is 36 more than the smaller angle. what is the measure of the larger angle?

Find the root(s) of f (x) = (x- 6)2(x + 2)2.

Percy rides his bike 11.2 miles in 1.4 hours at a constant rate. write an equation to represent the proportional relationship between the number of hours percy rides, x,and the distance in miles, y, that he travels.