Question 763594
Average of July - Sep (let's represent the months as J, A and S) is 180.

So J + A + S = 180*3 = 540   ----- eqn (1)

Average of Aug - October (let's represent the months as A, S and O) is 185.

So A + S + O = 185*3 = 555    ----- eqn (2)

170 were present in October, so O = 170.

Substituting for O in eqn(2), A + S + 170 = 555, so A + S = 555 - 170 = 385 --- (3)

Now, substituting for (A+S) in eqn (1)

J + (A+S) = J + 385 = 540, so J = 540 - 385 = 155.

No. of workers in July = {{{highlight(155)}}}


:)