Earthquake Wave

We learned some knowledge about earthquake wave from the PPT. Here is a picture for earthquake wave.

Seismic waves are waves of energy that travel through the Earth‘s layers, and are a result of earthquakes, volcanic eruptions, magma movement, large landslides and large man-made explosions that give out low-frequency acoustic energy. Many other natural and anthropogenic sources create low-amplitude waves commonly referred to as ambient vibrations. Seismic waves are studied by geophysicists called seismologists. Seismic wave fields are recorded by a seismometer, hydrophone (in water), or accelerometer.

Math Journal Assignment

When I first saw this question, the only thing I thought is what is the relationship between N(t) and t. Then I look though the question and found the thing that I want. It told me N(t) = 150 – 10t and what are N(t) and t.
I think these are typical questions.
b) Determine the value of N(-5).
d) What was the average temperature if 190 cups of hot chocolate were sold?
For question b. I think I should translate it first. Here is my result of translation. t is equal to -5 so we use -5 to replace t. Then N(t) is equal to 150 – 10X(-5). So we can know what N(t) is equal to easily.
For question d. I translate it first too. This time we know N(t) is equal to 190 and the only thing we need to do is finding out what is t. So here is the result.
190 = 150 – 10t . Now we need to know what is t. It is easy to solve.
In my opinion, everyone should translate the question firth with the information the we are told. Then solving this problem becomes easy.