La Adivinanza de la Semana

Las adivinanzas se complican cada vez más, aunque no dejan de ser fáciles. Aquí tenemos la de esta semana, si lo lees atentamente, veras que fácil es: One day a cat fell down a well. The well was eighteen feet deep. When the cat tried to climd out, it found that the sides of the well were very damp and slippery. However, with patient determination it finally managed to climb out. It took the cat one minute of climbing to gain three feet. However, after climbing for a minute, the cat had to rest for a minute before it could go on. During each minute of rest, the cat slid back two feet. How long did it take for the cat to get out of the well? Pide ayuda a tu profesor de matemáticas, si crees que lo necesitas. Good Luck