Question 364998
The sum of the digits of a positive 2-digit number is 13 If twice the first digit is 1 less than the second digit, what is the two digit number?

Let x = the unit's digit as the first digit
    y = the ten's digit as the second digit

1st equation
x+y = 13

2nd equation
2x = y-1
y = 2x+1

Substituting y=2x+1 in equation 1 gives us
x+(2x+1)=13
     3x =13-1
      x =4

Then y = 13-4=9

The 2-digit number is 94