You can put this solution on YOUR website! The sum of the digits of a positive two-digit integer is 45 less than the integer.
What is the tens digit of the integer?
Let x = 10's digit
Let y = units
10x + y = the two digit integer
x + y = 10x + y - 45
Subtract y from both sides
x = 10x - 45
Add 45, subtract x, from both sides
45 = 10x - x
45 = 9x
x = 5 is the tens digit