Following the formula above if you want to get degrees Celsius you have to subtract 32 from degrees Fahrenheit multiply the result by 5 and divide it by 9.
So in case with 6 we have: ((6 - 32) × 5) ÷ 9 = (-26 × 5) ÷ 9 = -130 ÷ 9 = -14.444444444444 °C