4,000,000 and 20,000,000 miles²
let x be the area of one desert then 5x is the area of the other
sum = x + 5x = 24,000,000
6x = 24,000,000
divide both sides by 6
x = 4,000,000
one desert is 4,000,000 miles²
and the other is (5 × 4,000,000)= 20,000,000 miles²
