Answer:
212F = 100C = boiling point at standard temp and pressure.
So from F to C first subtract the 32 degrees difference at freezing, then multiply the ratio of C:F which would be 100:180.
So 212-32=180F
And 100/180 is 5/9
So 180F x 5/9 = 100C
Remember: (F-32) x 5/9 = C
the opposite: (C x 9/5) + 32 = F