Find the height of the tree to the nearest foot

Looking at the triangle, we see that the angle 29.7 deg and the "adjacent side" length 20 ft are given.  Our job is to find the "opposite side," which is the height of the tree.

Write out the tangent function:    tan 29.7 deg = opp side  /  adj side

Then tan 29.7 deg = (opp side) / (20 ft).

Solving for the length of the opp side:

opp side = (20 ft)(0.57) = 11.41 feet.  This is also the height of the tree.