It does help to draw a picture, like the question suggests.
The two “triangles” (the second one is inside the first) formed by Julie and the tree and their shadows are similar triangles, meaning that they have proportional leg lengths.
Therefore, you can make a ratio between each triangle’s pair of legs (i.e. AB:BD and EC:CD).
The tree’s shadow is a sum of Julie’s shadow and the distance between them, so its length would be x + 56 feet.
You would set up the ratios in order like so:
AB EC
BD equals CD
(Imagine there are fraction lines between AB/BD and EC/CD.)
You can solve the unknown factors in the ratio by cross-multiplying and isolating x:
i.e. if AB = x
x EC
BD equals CD becomes CD*x = BD*EC.
If there are two instances of x (like “x” and “x + 56” in the case of this problem), you can subtract one from the other to “isolate x” (i.e. 3x = x + y becomes 2x = y).