Thirty percent of all the students in a school are in a play. All students except for 140 are In the play.
Let x = the total number of students, and p = number of students in the play.
If 30 percent of students are in the play:
.3x = p
If All except for 140 are in the play:
x - 140 = p
Now we have 2 equations, so use substitution to solve for x:
x - 140 = .3x
x - .3x = 140
.7x = 140
x = 140 / .7 = 200
Now that we know x, solve for p:
200 - 140 = p
60 = p
There are 200 students total, and 60 in the play.