Hey there! I'm happy to help!
To find the distance between two points, you find the difference between the y and x values, square them, add them, and then find the square root of that.
We subtract our y values.
-3-4=-7
And then our x values.
-6-9=-6
We square these values.
-7²=49
-6²=36
We add these.
49+36=85
And we find the square root, giving us √85.
Have a wonderful day! :D