Answer:
The number is 67
Explanation:
Equations
Let's consider the number 83. The tens digit is 8 and the unit digit is 3. Note the tens digit's addition to the number is 80, and the unit's addition is 3. This means the tens digit adds 10 times its value, that is, 83 = 8*10 + 3.
Now, let's consider the number ab, where a is the tens digit, and b is the unit digit. It follows that
Number=10*a+b
The question gives us two conditions:
1) The sum of a two-digits number is 13.
2) The tens digit is 8 less than twice the units digit.
The first condition can be expressed as:
a + b = 13 [1]
And the second condition can be written as:
a = 2b-8 [2]
Replacing [2] into [1], we have:
2b-8 + b = 13
Operating:
3b = 13 + 8
3b = 21
Solving for b:
b = 21 / 3 = 7
Substituting into [2]:
a = 2*(7) - 8 = 6
Thus, the number is 67