The temperate in Anchorage, Alaska at 9am was at -2°F. At 9pm the temperature decreased 7°F. Write an expression that represents the difference between the temperature from 9am to the resulting temperature at 9pm. How do I write the expression?

T=(-7/12)t-2

Im calling temperature T and time t for our equation but they can just as easily be Y and X

In 12 hours time the temp decreased 7 degrees so to get the slope we went down 7 and over 12 making it -7/12 (since we went down)

The at the starting point of t=0 it’s already -2 F making that our “y intercept” T intercept in this case

y=mx +b

In our case y=T x=t m=-7/12 and b= -2
Replace them to get
T=(-7/12)t-2

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