Question

Find the slope and the y-intercept of the line. y=9x-3

Answer 1

Slope = 9 

Y- intercept =  - 3

Answer 2

Basically, every linear function can be expressed as:
$y=ax + b$, where $a$ is the slope.

So, the slope is 9 in your case.

To find y-intercept of the line you have to set $x=0$ because line intercepts y-axis when $x$ is equal to zero:
$y=9*(0) - 3$

From here we can say that $b$ is the y-interception.
So, y-interception is -3 in your case.