

Given F = C*9/5 + 32
=> F-32 = C*9/5
=> C = {5*(F-32)}/9 .............1
Now put F = 68 in equation 1, we get
C = {5*(68-32)}/9
=> C = (5*36)/9
=> C = 5*4
=> C = 20
Again put F = 77 in equation 1, we get
C = {5*(77-32)}/9
=> C = (5*45)/9
=> C = 5*5
=> C = 25
So range of solution is kept it between 20° C and 25° C
