In any question where you have two points, (x1,y1) and (x2,y2), and you want to find the distance between them, the triangle will be one like I describe above. The hypotenuse is always the distance between the points. There is an equation that goes with this;
(square root of) (x1-x2)^2 + (y1-y2)^2,
but that equation is saying the same thing as "find the length of the hypotenuse of the right angled triangle above".
If there are already lines and/or triangles drawn in the question, ignore them and focus on this.