Add, divide- turn division equation into a fraction, boom
you can use 3 quarters and 2 pennies
You can use the distance formula:

To figure out what the distance between the points is. Our x1 is -1, and our y1 is 3. Our x2 is 7, and our y2 is -3. Then, we can just plug it in, and solve:

Simplify:

Simplify Further (S is the distance):

So, the answer is D, 8 units. If you want me to explain what I did, just tell me, I sure will! :) Anything still unclear?
Yes it is true as long as long as the corresponding sides are congruent they are similar.