Jeff observed that 60% of people at the mall shop for cloths on a particular day. if 25000 people did not shop for cloths that day the number of people who shopped for cloths that day ?

If 60% of people shopped for clothes, then 40% did not shop for clothes.
and 25,000 did not shop for clothes...

so 40% of the total people is 25,000
0.40x = 25,000
x = 25,000 / 0.40
x = 62,500 total people

so if the total people is 62,500 and 25,000 of them did not shop for clothes, then (62,500 - 25,000) = 37,500 <== shopped for clothes

Iam thinking the answer is a.) knew