What we have here in the picture is a graph of a segment. The goal is to find the segment's length, which we can do by using the distance formula:
Note that the distance between two points is equal to the length of the line segment that joins them.
So now we already have answers for two of the boxes.
The difference in the x-coordinates gives us the horizontal distance between the two points, while the difference in the y-coordinates gives us the vertical distance between the points.
So, the other two boxes should contain:
Just 7 would be the answer
One really simple way to find an equivalent fraction is just to multiply the numerator and denominator.
For example, for the first answer, 
, I simply multiplied the numerator and denominator each by 2. This gives you an equivalent fraction.
You can then continue with this process using numbers such as 3, 4, 5, and 6 as your multiplication factor.
Pythagoras, cool.
30^2 is 900
15^2 is 225
26^2 is 676
676+225 isn't 900 so it isn't A.
10^2=100
26^2=676
24^2=576
100+576=676 so B is a right angled triangle.
Hope this helps :)
