Explanation:
that is just to be read from the chart.
a)
we see Kiev has 1° C.
Oslo has 2° C.
what is the difference ? 2 - 1 = 1°
b)
don't get confused.
the chart says temperatures at midday.
6 hours later IS 6pm.
the temperature in Kiev raises during that time from 1° up by 6°.
that means the temperature there is then 1 + 6 = 7° C at 6 pm.