By counting the number of squares under each continent we can get to know the areas as follows

Africa = 26 sq. units

Europe = 10 sq. units

Australia = 8 sq. units

Asia = 44 sq. units

Antarctica = 13 sq. units

North America = 17 sq. units

South America = 18 sq. units

(a) ratio of area of Africa to Europe = =

Divide numerator and denominator by 2 we get

ratio of area of Africa to Europe = = 13:5

(b) ratio of area of Australia to Asia = =

Divide numerator and denominator by 4 we get

ratio of area of Australia to Asia = = 2:11

(c) ratio of area of Antarctica to combined area of North America and South America = = = = 13:35