Let us assume the number regular memberships = x
Let us assume the the number of off-peak membership = y
Then
x + y = 420
y = 420 - x
And
80x + 60y = 31100
Replacing the value of x from the first equation in the second equation, we get
80x + 60y = 31100
80x + 60(420 - x) = 31100
80x + 25200 - 60x = 31100
20x = 31100 - 25200
20x = 5900
x = 5900/20
= 295
From the above deduction, we can conclude that 295 regular memberships were taken last month. The correct option among all the options that are given in the question is the fourth option or option "D".
