I'll let the words of Kristin Levine from her novel The Lions of Little Rock (pg. 269-270) speak for themselves:
"[Mr. Harding, the math teacher,] pulled out a pencil and started to write on a blank piece of paper before me. "I think what's happened, Marlee, is that you've realized the world isn't an addition problem."
He wrote 3 + 4 = 7 down on the paper. "We tell kids that sometimes. We pretend the world is straightforward, simple, easy. You do this, you get that. You're a good person and try your best, and nothing bad will happen.
"But the truth is, the world is much more like an algebraic equation. With variables and changes, complicated and messy. Sometimes there's more than one answer, and sometimes there is none. Sometimes we don't even know how to solve the problem."
He wrote x^2 + 4x - 21 = 0.
"But usually, if we take things step by step, we can figure things out. You just have to remember to factor the equation, break it down into smaller parts."
I stared at x^2 + 4x - 21 = 0. Pictured it factored into (x - 3)(x + 7) = 0. Imagined the solutions, x = 3 and x = -7, and felt a little better.