We are given
For Monday:
Morning temperature =68 F
but, by the afternoon, the temperature had risen 18 oF
so, afternoon temperature =68+18=86F
For Tuesday:
the temperature had dropped 21 oF since Monday afternoon
so, morning temperature=86-21=65F
but rose 20 F by the noon
so, noon temperature =65+20=85F
now, we can find temperature difference
temperature difference = 85F-68F
temperature difference = 17F.......................Answer
