【12】Measure the depth of a well with a rope. When the rope is folded four times to measure, 3 meters of the rope protrude above the well; when the rope is folded five times to measure, the rope is 1 meter short of reaching the well's mouth. The depth of the well is ( ) meters; the length of the rope is ( ) meters.
【Key Points】Profit and Loss Problem.
【Analysis】Well depth: $(4 \times 3+5 \times 1) \div(5-4)=17$ (meters); Rope length: $(17+3) \times 4=80$ (meters). 【Answer】Well depth 17 meters, rope length 80 meters