蜗牛从井底往上爬，白天向上爬120 厘米，晚上下滑77 厘米，到第8 天爬到了井口。猜一猜，井深是多少厘米？,U8V;]'q(J)B3J2c4R.m8R)Q(U6~0k
算式：提示0W/Q7K1`2l'y8t1p'T'm2j,U8V;]'q(J)B3J2c4R.m8R)Q(U6~0k
答：井深是/g4{1c-O6R9J0@4?+L1P+a厘米。,U8V;]'q(J)B3J2c4R.m8R)Q(U6~0k