Answer: 24 minutes of commercials.
Step-by-step explanation: Divide 90 by 30 to figure out how much you're going to multiply the 8 minutes of commercial by.
The answer is three, then multiply three by the 8 minutes of commercial to get the answer for how many minutes a commercial will be if there were 90 minutes of TV air time.
For every 30 minutes there are 8 minutes, so you just multiply the constant figure which is three by the number that has not yet been changed.
