The answer to your problem is C. You start out at zero. The red line goes from 0 to 3, hinting that the first part of your expression is a positive three. The blue arrow points towards the -4. The difference between 3 and -4 is 7, and since the line goes backwards, that means that the 7 in your expression is actually a negative. This provides you with answer C: 3-7.
This is Pythagorean's Theorem, with one leg being 10 and the hypotenuse being 16. Using those values in the theorem looks like this: and and so Take the square root of both sides to find that b = 12.5
