A literal equation is an equation where variables represent known values.
One example of a literal equation would be;
• Solve Q = 3a + 5ac for a
I need to get the variable a by itself. Currently, it's multiplied onto other stuff in two different terms. I can't combine those terms, because they have different variable parts. (The first term has no other variable, but the second term also has the variable c.) I want to divide off the stuff that's multiplied on the specified variable a, but I can't yet, because there's different stuff multiplied on it in the two different places. But what if I factor the a out front?
The "trick" came in the second line, where I factored the a out front on the right-hand side. By doing this, I created one (big, lumpy) multiplier on a, which I could then divide off.