Whats the digit?

Question

The sum of the digits of a 2-digit number is 8. if the tens digit is 4 less than 5 times one digit, what is the number?

Answer 1

A two digit number contains a tens digit and a one's digit.  We define variables for each digit.

 

Let the tens digit = x

Let the ones digit = y

 

Using these variables, we can write equations.

 

x + y = 8              eq1

 

x = 5y - 4              eq2

 

 

We can substitute eq2 into eq1.  This will allow us to get an equation in terms of only y,

 

(5y - 4) + y = 8

 

 

Solve for y from this equation.

 

6y - 4 = 8

 

 

Add 4 on both sides of the equation.

 

6y = 12

 

 

Divide both sides of the equation by 2.

 

y = 2

 

 

Since the ones digit is 2, that means the tens digit is 6.  The number we get is 62.

 

 

 

 

Answer 2

ab is the number

a+b=8

a=5b-4

substitute

5b-4+b=8

6b-4=8

6b=4+8

6b=12

b=12/6

b=2

a+b=8

a+2=8

a=8-2

a=6

62 is the number