The formula F = 1.8 C + 32
gives an approximate conversion of degrees Cantigrade to Fahrenheit
We are asked to find which is the temperature for which the readout of C (degrees centigrade) equals the readout in F (Fahrenheit):
Then we assume that C anf F (variables in the equation) have the same value . That is C = F and replace one with the other to solve for one single unknown:
the equation then becomes:
C = 1.8 C + 32
we group all therms with C on the left:
C - 1.8 C = 32
now combine like terms:
- 0.8 C = 32
and finally divide both sides by "-0.8":
C = 32 / (-0.8)
C = - 40 degrees
This is the temperature for which both readings agree.