# How do I find the Y coordinate? #y = -2x+9# and #-x-y=-1#

##### 1 Answer

This is a system of simultaneous equations.

#### Explanation:

Call the two equations:

Equation 1:

Equation 2:

Multiply both sides of Equation 2 by

Subtract

Now, we can substitute this value of

Multiply out the parentheses:

Collect like terms (which involves subtracting

Multiply both sides by

We could also solve to find the value of

It's worthwhile and interesting to realise that these two equations are the equations of straight lines, and the