Let A be the set of population travels by car(in percentage) and
B be the set of population travels by bus(in percentage).
Then A⋂B is the set of population travels by car and bus and
A⋃B is the set of population travels by car or bus.
Then,n(A) = 20 , (B) = 50 ,n(A⋂B) =10
n(A⋃B) = n(A) + n(B) - n(A⋂B)
= 20 + 50 - 10
= 60
∴ The set of population travels by car or bus is 60%