How come 10x + y - (x+y) = 9x

Hi Guys,

I cant remember my school maths and am trying to work out how come "10x + y - (x+y) = 9x".

I know this is very basic but can you pls give me a step by step breakdown?

tnx!

Sure.

10x + y - (x+y) = 9x

Step 1. Distribute the negative.

10x + y -x -y

Step 2: Using PEMDAS, simplify,

10x -x ( The y's go away).

=9x.

Distribute the - which is actually -1 and then add the common variables(i.e. 10x+-x, y+-y) You get 9x and that equals 9x.

10x+y-x-y=9x
9x=9x
1=1