So, Kaylee, if I owe you 10 oranges (meaning I have -10 oranges) and then I owe you 4 more (-4 oranges), how many oranges do I owe you altogether? 14, right? I have -14 oranges.
As long as the variable is the same and with the same degree (can't do 10x - x2), you can add or subtract them as though they were oranges. 10x means 10 times x, or x + x + x + x + x +x + x + x + x + x. If I take 4x away, then I have 6x.
Instead, we are dealing with negative numbers. You already owe me 10 u's, meaning you have -10u. Now I'm saying you owe me 4 more u's, so now you are 14 u's in the hole. Your balance of u's is -14, which we write as -14u.
Anytime I have the same thing being multiplied, I can add or subtract! 10(200) + 5(200) = 15(200). Get it?
Hope this helps!
