Answer:
<em>n</em> - <em>k</em> + 1
Step-by-step explanation:
This is assuming (because you did not say) that <em>n</em> and <em>k</em> are integers and <em>n</em> is greater than <em>k</em>.
Example: from 2 to 5 {2, 3, 4, 5} includes 5 - 2 + 1 = 4 numbers.
Example: from -6 to 4 includes 4 - (-6) + 1 = 11 numbers, namely {-6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4}
Let us try and solve it analytically. We have that the side=x+3 together with the short side=s and the diagonal=x+4 satisfy the Pythagorean Theorem. Then we have that

. This yields

which yields s^2=2x+7, hence a) is the correct answer.
Answer:
adjacent
you can search it up it's one of the first pictures
The answer is b=-1 hopefully the s up so you can see my work and understand how I did it.