How do you subtract negative 18 degree celsius from 86 degree Fahrenheit?

Answer 1

86 deg F = 30 deg C

So the temperature has changed from -18 deg C to 30 deg C, an increase of 48 deg.

Conversely,

-18 deg C = -0.4 deg F

So the temperature has changed from -0.4 deg F to 86 deg F, an increase of 86.4 deg.

Answer 2

First, convert 86°F to Celsius: (86°F - 32) * 5/9 = 30°C. Then, subtract 18°C from 30°C, which gives 12°C.