The distance between points $ A $ and $ B $ is :
$$ d(A, B) = 1 $$To find distance between points $ A(x_1,y_1)$ and $ B(x_2,y_2)$, we use formula:
$$ \color{blue}{ d(A,B) = \sqrt{(x_2 - x_1)^2+(y_2 - y_1)^2} } $$In this example we have:
$$ \begin{aligned} & A \left(-5,~6\right) \implies x_1 = -5 ~~\text{and}~~ y_1 = 6 \\[1 em] & B \left(-6,~6\right) \implies x_2 = -6 ~~\text{and}~~ y_2 = 6 \end{aligned} $$Substituting $ x_1 $, $ x_2 $, $ y_1 $ and $ y_2 $ into the formula above yields:
$$ \begin{aligned} d(A,B) & = \sqrt{\left( -6 - \left( -5\right) \right)^2 + \left( 6 - 6 \right)^2} \\[1 em] d(A,B) & = \sqrt{ (-1)^2 + 0^2 } \\[1 em] d(A,B) & = \sqrt{ 1 + 0 } \\[1 em] d(A,B) & = \sqrt{ 1 } \\[1 em] d(A,B) & = 1 \end{aligned} $$