Question 132905
Your answer is correct!  Let's see how we get it.
Using the Pythagorean theorem on the right triangle whose height is that of the tree (50 ft.) and whose base is your distance from the base of the tree (120 ft.) The hypotenuse (c) is the distance you are looking for.
{{{c = sqrt(120^2+50^2)}}} 
{{{c = sqrt(14400+2500)}}}
{{{c = sqrt(16900)}}}
{{{c = 130}}}ft.