Is (2,10) a solution of the equation y = 9x

No.

This line is already in slope-intercept form.

The slope of the line is 9, and the y-intercept is 0.

Because of this, we can find every y value for any x value simply by replacing x with the value of the x coordinate.

By replacing x with 2, we can see what the y coordinate would be when x is 2.

9 (2) = 18

The y value would be 18, which is not 10, meaning (2, 10) is not a solution to the equation.