The rose on the temperature from 6 a.m. until noon is given by the product between the rate it rises by the amount of hours it took to rise. From 6 a.m. until noon, we have 6 hours
[tex]12-6=6[/tex]And the rate it rose was 1.2 °C per hour, then, the increase in the temperature is given by
[tex]6\cdot1.2=7.2[/tex]The same idea goes from the drop of the temperature from noon to 6 p.m.
Between those instants, we have 6 hours again(6 p.m. = 18h)
[tex]18-12=6[/tex]And the rate it dropped was 0.8 °C per hour. The fall in the temperature is given by
[tex]6\cdot0.8=4.8[/tex]And finally, to get our answer, we just need to add the temperature increase to our initial temperature, and then, subtract the drop we had after.
[tex]T=-5+7.2-4.8=-2.6[/tex]The temperature at 6 p.m. was - 2.6 ºC.
