60 % of the people did buy shirts and 2500 people didn't buy shirts how many shirts did they buy?

Well it says that 60% bought so 40% did not. lets represent total people with t. s will be shirt people and n is non shirt people.

we know n = 2500 people

we also know total people equals non shirts and shirts added together. so:

t = n + s or

t = 2500 + s

we also know that n is 40% of t and that n = 2500 so

n = 40% * t or

2500 = 0.4 * t

t = 6250

we knew earlier that

t = n + s, so

6250 = 2500 + s

s = 3750