Use substitution method for y=10x-9 and y=x+18

x=3

y=21

Step-by-step explanation:

To use substitution method, first we need to decide which variable solve first, either x or y.

Here we decide to start by 'y' using equation y=x+18, which is already solved for 'y'

That same equation is then substitute into the first equation:

x+18= 10x-9

From here, we isolate 'x' variable and grouping terms, we have this:

27=9x

Resulting x=3

Now, we can use the above result in the second equation (y=x+18)

Leading to y=3+18=21.