The tempature is -3 degress. the temperature is expected to decrease 2.5 degress each hour until the temperature reaches -18 degress. how many hours will it take to reach -18? a 6hours b 7 hours c 7.2 hours d 8.4 hours

We can set this problem up as an algebraic equation, which we can then solve to find our answer.

We start at -3. So we can start our equation with that:

However, this doesn't represent any change in temperature, just that we start at -3. To show change, we will use the variable , where stands for the number of hours. Each hour accounts for a change of -2.5 in degrees, meaning that we must multiply our by -2.5. We can now add this term into our equation:

We are trying to find when we will reach -18 degrees, so we will set our entire equation equal to -18 and solve:

It will take us 6 hours, or choice A.