Net change from the first to the second is found by subtracting the first from the second.
a) Mars - Neptune = (-60 °C) - (-214 °C) = (-60 +214) °C = 154 °C
b) Neptune - Earth = (-214 °C) - (14 °C) = -228 °C
c) Earth - Venus = (14 °C) - (460 °C) = -446 °C