The formulas for temperature conversion are

#"C" = 5/9("F - 32")# and #"K = C + 273.15"#

**1.** Convert #"98.6 °F"#

#"C" = 5/9("F - 32") = 5/9(98.6 – 32) = 5/9 ×66.6 = "37.0 °C"#

#"K = C + 273.15 = 37.0 + 273.15 = 310.2 K"#

**2.** Convert #"-5.00 °F"#

#"C" = 5/9("F-32") = 5/9("-5.00 – 32") = 5/9("-37.00") = "-20.56 °C"#

#"K = C + 273.15 = -20.56 + 273.15 = 252.59 K"#

**Note:** The above formulas ignore units. With units, the formulas become

#"C" = "5 °C"/(9 color(red)(cancel(color(black)("°F"))))("-5.00 - 32") color(red)(cancel(color(black)("°F"))) = "-20.56 °C"#

and

#"K" = "-20.56" color(red)(cancel(color(black)("°C"))) × "1 K"/(1 color(red)(cancel(color(black)("°C")))) + "273.15 K = 252.59 K"#