You will get the answer by cross multiplication
Length..............width
32.....................24
x..........................3
24x = 32 × 3
x = 32 × 3 / 24
x = 4
Therefore, the length of the postcard = 4 in
14 days = 2 weeks
20weeks : 14 days = 20 weeks : 2 weeks = 20 weeks / 2 weeks = 10:1
hope it helps!