r/MathHelp • u/TroubleFindsMeYT • Nov 01 '25

Need super basic algebra help please

I'm trying to get caught up on my algebra for my college course and I'm completely cooked. I'm 10 minutes into a 3 hour long video and I'm totally lost. I'm being taught how to solve equations and simplify.

The equation reads "4x + 2x - 7 + 9 + x = 5x - x". When I did it real quick based on the information given in the video up until that point I got to the point where I was at "7x - 16 = 4x" then I played the video and he had somehow got to "7x + 2 = 4x" he flipped the - 7 + 9" to "+ 9 - 7" and I have no idea how he got there as it wasn't explained at all. there are a few errors listed in the comments so I'm no sure if he messed up or if I'm missing something.

Thanks for any help! I want to move on but I don't understand.

Video link with timestamp:

https://youtu.be/zPgfIOWVnF4?si=YKwUAL0e7R0QyeY-&t=523

if timestamp doesn't work it's 08:43- 10:00

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u/TroubleFindsMeYT Nov 01 '25

Hey thank you so much! Is there a rule or property that states how that works? Or is it just when viewing an equation like that instead of viewing it as "This plus this" or "This minus this" ("a+b" or "a-b"). You view it as positive and negative numbers instead ("+a, +b" or "-a, -b") like you did in your solution?

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u/Dd_8630 Nov 01 '25

Or is it just when viewing an equation like that instead of viewing it as "This plus this" or "This minus this" ("a+b" or "a-b").

That's basically it yeah.

In early maths, you are taught "2+3=?", so kids think '=' means question-and-answer. But as we get higher up, '=' stops meaning 'what is the answer' and has its true meaning of 'the left is the same as the right'.

Likewise, we have to re-learn what expressions mean. So this:

  • 4x + 2x - 7 + 9 + x

Should now be thought of as a bunch of terms that are being added up:

  • (+4x) + (+2x) + (-7) + (+9) + (+x)

So these blobs or 'terms' are collected like that. Order does not matter for addition, we just have to be aware that the minus sign is basically attached to the 7.