What do you need help clarifying? Did you want to go over the questions you missed? (:
The locomotive is 40 ft long.
40 ft = 40 * 12 in. = 480 in.
The locomotive is 480 inches line.
The model is 16 inches long.
480/16 = 30
The real locomotive is 30 times longer than the model.
A window on the locomotive is 30 times wider than a window on the model.
A -120 difference will be seen in the temperature within a 7 hour period
<u>Equation</u>
<em>-</em>30 x 7
<em>Multiplying two of different signs ( - + , + - ) will always be negative.</em>
<em>Multiplying two of the same sign ( - - , + + ) will always be positive.</em>