The answer on page 4.7.8 of the seventh grade math book 1 13 published by People's Education Press.

This is a complete solution from middle school textbooks.

Solution: We go to the swimming pool for X times, and pay Y 1 yuan with membership card, and Y2 without coupons, so Y 1=80+X, Y2=3X.

Solution: Go to the swimming pool X times and pay the same money as if you had a membership card.

Equation 80+x=3x can be listed.

Find x=40.

So going to the swimming pool 40 times with a membership card is the same as not having a membership card.

Then it is more cost-effective to apply for a membership card for more than 40 times than not to apply for a membership card.

Then it is more cost-effective not to apply for a membership card within 40 times than to apply for a membership card.

2. Solution: After setting X minutes, the hour hand and minute hand of the clock coincide.

List the equation x/60*360=x/60*30+90.

X= 180/ 1 1 min.

After setting y minutes, the hour hand and minute hand of the clock form a right angle.

List the equation y/60*360- 180=y/60*30+90.

The solution is y=540/ 1 1 min.

Z minutes later, the hour hand of the clock is at right angles to the minute hand.

List the equation z/60*360-90=z/60*30+90.

The solution is z=360/ 1 1 min.