To protect the wall from your forehead, you need to know how to think it through.
Solve for x means we are being asked to write x=?
What we are given contains x in 2 places, on either side of the equal sign.
When both sides are equal we can perform the exact same operation to both sides.
For instance 5=5
If we subtract 3 from both sides we'll have 5-3=5-3 which is 2=2
The sides may not be what they were originally but they are still equal.
Hence
has x on both sides.
To get the x's on the same side, subtract bx from both sides,
the two sides will still be equal...
therefore we have
If you have 5 boxes of apples, 20 apples per box
and you give 3 boxes to your sister, how many apples will you have ?
You can calculate 100-60=40 or 2(20)
You get the same answer.
Hence we get x in one place by factorising as above.
This is "x multiplied by both a and -b".
To move the (a-b) away from the x, to leave x standing alone,
we divide both sides by (a-b), just as
As
this is
Hence