Cho ba vị từ P(x), Q(x), R(x) xác định như sau: P(x) = {x  4}, Q(x) = {x + 3 là số lẻ}, R(x) = {x+ 2 < 5}

In a two-digit number the units' digit is 7 more than the tens' digit. the number with digits reversed is three times as large as the sum of the original number and the two digits. find the number.