Growing Tree
When Mrs. Johnson's class planted a tree, it was 9 feet high. Each year, including the fourth year, the height of the tree increased by x feet. During the fourth year, the height of the tree increased by onesixth the height it had reached at the end of the third year. How many feet high was the tree at the end of the fourth year?
(Source: Adapted from Mathematics Teaching in the Middle School, MarApr 1997)
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