BdMO Online Forum

Notice when the symbol $ "<" $ is inserted in the appropriate place which is between the eight digits, there are $7$ place to put that symbol inside the eight digits. Also we've given a condition that "each number has $6$ digits in such place where that digit is less than the next digit", so I've to put $6$ symbols in that $7$ places. I can do that $\binom{7}{6} = 7$ such ways. And that's the answer I think. :/