Scale 'n' Pop
To scale your balloon, type a fraction into the box and then click on the Scale button; your balloon's new size will be displayed. When you think your balloon is the right size to reach the nails, click on the Release button. If your balloon doesn't pop, click on the Reset button, try a different fraction, and then scale and release it again. Repeat those steps until you win the game.
Remember to try all three balloon booths!