Height of tall tree = 4 foot
Height of shorter tree = 1 foot
Explanation:
The taller tree is 1 foot shorter than five times the height of the smaller tree.
Let the height of smaller tree be h in foot.
 Height of taller tree = 5h -1
If she's stacked the shortest tree on top of the taller tree they would be a total of 60 inches tall.
 That is h + 5h -1 = 5 foots
 6h -1 = 5
 6h = 6
 h = 1 foot
 Height of taller tree = 5h -1 = 5 x 1 - 1 = 4 foot
Height of tall tree = 4 foot
Height of shorter tree = 1 foot