V T = k
*** IF *** I assume this is true then:
500 * 2.5 = k = 1250
so
100 T = 1250
T = 12.5 C
I guess that is the answer they want, but in fact V T = constant ONLY if you use degrees KELVIN which is degrees C + 273
so really
500 * 275.5 = k = 137,750
so
100 T = 137,750
T = 1377.5 Kelvin
= 1104 Centigrade