A piece of copper wire if it is initially 2.11cm long and it changes to 20.12 cm long. What is the change in temperature if the coefficient of linear expansion is 16.66x10^-6 oC
I suspect a typo. No way is a wire going to increase in length by a factor of 10.
Also, your coefficient is lacking some units.
In any case, if it grows by 16.66*10^-6 cm for each °C, just divide the length increase by that number.