3x + 7 = 4t - 3
7x(7+1) - 3t(5-12x)
Okay, so what is different about the above and why does it matter?
Answer: One you can solve, and one you can manipulate (such as simplify).
A really good way (and the way I use) to remember is that equations have an equals (=) sign.
3x=5 -> “3 x equals 5″.
With an equation, we seek a solution set (if it exists). Expressions, however, are something you can manipulate.
Equations we solve, expressions we manipulate.