The options you gave are extremely confusing, but if you round 7.9 it is 8, and if you round $3.89 it is $4. Therefore, the best estimate would be 8•$4, or $32
The distance formula is:

We are given two points in the form (x,y), so plug in the values to the distance formula:

Next we can simplify. We know that 12-12 is 0, so we can drop it from the equation, as it will not affect our answer. Also, we know that -10-15 is -25:

The square and square root cancel each other out leaving us with 25.
The answer is 25.
75.
Explanation: from 3 to 12, you add 9, and then double the 12 to get to 24, and then add 9 again to get to 33, and double it to get 66, so the pattern is to add 9 and then double.