The tens digit of a two-digit number is 5 more than twice the ones digit. The sum of the digits is 8. What is the number?

Answer 1

let a be in the one's position and b in the tens position

b=5+2a

a+5+2a=8

a=1 and b=7

the number is 17.

Answer 2

Great question!

Let's start by making the two digits of the number as a for the tens and b for the ones. Number ab.

We know that a=5+2b and that a+b=8 from the question.

This allows us the set up a system of equations, which you can solve several ways.

I took the second equation and subtracted b from both sides, giving me a=8-b

Now you can set the two equations equal to each other since they both equal a.

5+2b=8-b

5+3b=8

3b=3

b=1

Now go back to a=8-b

a=8-1

a=7

We know that the original number is 71.