Question

Can any body explain this question and answer.
Is the answer right?

Among 200 people, 150 either swim or jog or both. If 85 swim and 60 swim
and jog, how many jog?
SOLUTION:
Let U be the set of people considered. Suppose S be the set of people who
swim and J be the set of people who jog. Then given n(U) = 200; n(S ∪ J) = 150
n(S) = 85; n(S ∩ J) = 60 and n(J) = ?
By inclusion - exclusion principle,
n(S ∪ J) = n(S) + n(J) - n(S ∩J)
150 = 85 + n(J) - 60
⇒ n(J) = 150 - 85 + 60
= 125
Hence 125 people jog.