Amazing Alex The Backyard level 2-21, called “Underwater Adventure”, is rather challenging. Place the 8-ball in the slingshot. Angle a shelf slightly upward just left of the second balloon, and place the scissors just above the balloons on the extreme right. Place one more balloon just left of the bottom star. Hopefully everything goes well and the cardboard box actually reaches the ground.
If you have a different strategy for completing this level feel free to leave a comment below.