If we let x be Cody's height on the first day of the school last year then, his height on the first day of school this year can be expressed as,
y = x + 0.10x
y is given to be 165. Substituting this to the given equation,
165 = x + 0.10x
Simplifying,
165 = 1.1x
The value of x from the equation is 150 ft.
Answer: 150 ft.