Can We Add And Subtract "Like" Terms But We Cannot Add Or Subtract "Unlike" Terms. What Example Can You Think Of In Real Life That Demonstrates This Concept?

Like terms:
   3x + 4x = (3+4)x = 7x
Unlike terms:
   3x + 4x^2      (cannot be combined. The best you can do is factor out an x: (3+4x)x.)