Acold wave hit chicago when the temperature hit 62 f during the cold wave the temperature dropped 2 degrees every hour how many hours was it before the temputure was below 40 f

We start at 62 Fahrenheit. And every hour we drop two degrees. We want to know how long it took for the temperature to drop to 40 Fahrenheit.

If one hour passed, then the temperature dropped two degrees.
If two hours passed, then the temperature dropped 4 degrees.

See the pattern? We can define this as 2h. Where h represents time in hours.
We subtract 2h from 62. 

We can write this as a function. F(h) = 62 - 2h.
Where F is the temperature in Fahrenheit. And h is the hour(s).

Now that we have the formula, let's plug in the value 40 Fahrenheit to see how long it took for the temperature to drop to 40 degrees.

40 = 62 - 2h
Subtract 62 from each side

-22 = -2h
Divide both sides by 2

h = 11

So, it took 11 hours for the temperature to drop to 40 Fahrenheit.