Sonjia bought a combination lock that opens with a 4-digit number created with the numbers 0 through 9. The same digit cannot be
used more than once in the combination. If Sonjia wants the last digit to be 7 and the order of the digits matters, how many ways can the remaining digits be chosen?
So the total amount of paper is 4/4 right? And she kept 3/4. So we have to minus 3/4 from 4/4. Because it has the same denominator we need not change it to similar one.So 4-3 is one. So answer is 1/4
