Question

`x + y = z" "` what is x?

Answer 1

A variable .

Explanation:

It is a variable from the first term in the expression or equation.

Answer 2

`x=z-y`

Explanation:

`color(blue)("Introduction to a mathematical method")`

This may already be known to you but stick with it.

The word equation has a direct link to the word equals as far as mathematics goes.

Stating the obvious but the highlighting of the fact is very important; the value on one side of the equals must be exactly the same as the value on the other side.

As an example: `5=5`

But we may if we chose write 5 as `3+2` so it would be true to write

`5=3+2`

What we do to one side of the equation we also do to the other side.

Subtract `color(red)(2)` from both sides

`color(green)(5color(red)(-2)" "=" "3+2color(red)(-2)`

`" "3" "=" "3+0`

`" "3" "=" "3`

The above is using the first principle method.

Shortcut methods are the same as first principle but they jump steps.
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`color(blue)("Answering the question")`

Given:`" "x+y=z`

subtract `color(red)(y)` from both sides

`color(green)(x+ycolor(red)(-y)" "=" "zcolor(red)(-y))`

`x+color(white)(.)0" "=" "z-y`

`x=z-y`