How is translating a figure on x-y coordinate axes like adding and subtracting using a number line?

When translating a figure, all you are doing is moving the x-y coordinates according to where it needs to go.  So, if it moves to the right, you are adding a number to the coordinates, or if it moves to the left you will be subtracting from the coordinates, just like when you add or subtract on a number line.

7. 17/99

for this one, you multiply your decimal by 100 to get you

100x = 17.171717..

then you subtract it from x = .171717 to get you

99x = 17

then you divide.

8. 0.5

The area of a square is the side length squared. You square root 0.25 to get you 0.5.