Question 12
Question 17. Each of the digits 1, 2, 3, 4, 5, 6 and 7 is placed, one to a box, to form the two 2-digit numbers and one 3-digit number in the arithmetic problem shown.
$$M=\boxed{\phantom{0}}\boxed{\phantom{0}}\boxed{\phantom{0}}-\left(\boxed{\phantom{0}}\boxed{\phantom{0}}-\boxed{\phantom{0}}\boxed{\phantom{0}}\right).$$
What is the least possible value of $M$?
$$M=\boxed{\phantom{0}}\boxed{\phantom{0}}\boxed{\phantom{0}}-\left(\boxed{\phantom{0}}\boxed{\phantom{0}}-\boxed{\phantom{0}}\boxed{\phantom{0}}\right).$$
What is the least possible value of $M$?