book Maths Puzzle Numerical Ability

Find the slope of the line through the pair of points.

(-9, -6) and (-9, -8)

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book Other Question

4y-3(y+8)=12 can you please show how an tell how to solve x^2-9y^2
_________ / (x^2-3xy)
7x^2+21y

This is what I have so far...

(x-3y)(x+3y) over (?) * (times) 1 over (x^2-3xy)

I cant figure out how to factor the denomoniator i