Cody was 165/,/text{cm}165cm165, space, c, m tall on the first day of school this year, which was 10/%10%10, percent taller than he was on the first day of school last year.

How tall was Cody on the first day of school last year?

Assume that Cody was x cm tall on his first day at school last year.

Assume that Cody is y cm tall on his first day at school this year.

This year, Cody became 10% taller.

10% is equivalent to 0.1

This can be translated into the following:

y = x + 0.1x

We are given that y = 165 cm.

Substitute in the equation to get x as follows:

165 = x + 0.1x

165 = 1.1x

x = 150 cm

Based on the above calculations, Cody was 150 cm tall on his first day at school last year.