Answer:
373 K; 253 K
0°C ; -258°C
Step-by-step explanation:
In order to change Temperatures to Absolute Value (Kelvin) you shoud do this sum:
T° in C + 273 = T° in K
For question 1:
100°C + 273 = 373K
-20°C + 273 = 253K
For question 2:
T° K - 273 = T° C
273 K - 273 = 0°C
15 k + 273 = -258 °C