The formula of a distance between two points:

We have the points (-3, 3) and (5, 0).
Substitute the coordinates of the points to the formula:

I think it's two but I'm not sure don't count on it.
0.5! This can be explained because 1/2 x 1/2 is equal to 0.25 so if we add another 0.25, it will be 0.5
19.164 can be rounded to 19.2. That is because 0.164 is closer to 0.2 than it is to 0.1
9.53 rounded the the nearest tenth is 9.5 because 0.53 is closer to 0.5 than it is to 0.6.
19.2 - 9.5 = 9.7
Your answer is 9.7
0.078= 78/1000 = 39/500
Simplified by dividing numerator and denominator by 2.
Hope this helps! :)