To find the net change in temperature, you can subtract the final temperature from the initial temperature.
The initial temperature yesterday was 7.5 degrees Celsius, and the final temperature today is -3 degrees Celsius.
Net change = Final temperature - Initial temperature
Net change = -3 - 7.5
Net change = -10.5 degrees Celsius
So, the net change in the temperature is -10.5 degrees Celsius. This means the temperature dropped by 10.5 degrees.