Let's see:
9 is the denominator, if we pass it to the other side it will be as multiplication.
Now, if we pass 5, the numerador, it will go as denominator.
Now just add 32 in both sides
Ok, this is the formula to discover the temperature in fahrenheit, now let's see the procedures:
A - Multiply both sides of the equation by 9/5, ok
Ad 32 to both sides of the equation, ok
B - Multiply 50 by 9, ok
Divide the answer by 5, ok
Add 32, ok
So both procedures will give the correct temperature.