Question: Kirsty's school locker has a two-digit number on it. The sum of the two digits is 10 and their difference is 2. If the locker number is less than 50, what number is it?
Let the two digits be d1 and d2. Then
d1 + d2 = 10
d2 - d1 = 2 (one of the digits will be larger than the other, so call that one d2)
add together the above two equations. This gives us,
2*d2 = 12 - now divide both sides by 2
d2 = 6, hence d1 = 4
The digits on the locker are 6 and 4. So the locker number itself must be 46 or 64.
Since we are told that the locker number is less than 50, then the locker number must : 46