An aluminum wing on a passenger jet is 37 m long when its temperature is 18C. At what temperature would the wing be 6 cm (0.06 m) shorter?

Here is what my professor said about my initial answer which was incorrect:

The textbook shows 25 x 10^6 as the correct constant. Try the calc again...you would have gotten it if you used the number. -49.6 is really close."