we let y = the degrees in Celsius and x = the degrees in Fahrenheit. 

The freezing point of water in Celsius is 0°.

The freezing point of water in Fahrenheit is 32°.

So one ordered pair is (x1,y1) = (32,0).

The boiling point of water in Celsius is 100°.

The boiling point of water in Fahrenheit is 212°.

So another ordered pair is (x2,y2) = (212,100).

So we find the equation of the line through those two points (ordered pairs).

We use the slope formula:



where (x1,y1) = (32,0)

and where (x2,y2) = (212,100)

After you find m (which will be a fraction, which you will reduce), substitute
it into

the point-slope formula:

y - y1 = m(x - x1)

where (x1,y1) = (32,0)

You finish this.

After you finish you might substitute C for y and F for x.

Edwin