How many minutes is it before 12 noon if 20 minutes ago it was three times as many minutes after 9 am

First, change everything into minutes.

12 noon is 12 by 60 which = 720 minutes.

9am is 9 by 12 which = 540 minutes.

X is now your number of minutes before noon. So noon - x is the next step:

720 - x

20 minutes ago it was 720 - x - 20

720 - x - 20 = 540 + 3x (3x because you're looking for 3 times as many minutes)

720 - 20 - 540=4x (you combine all the like numbers and variables)

160 = 4x

160/4 = x

40 = x

Your answer is 40 minutes