Question

the tens digit of a number is twice the ones digit. the sum of the digits in the number is 12. what is the number?

Answer 1

Hello,
Let's x the ones digits
2x is the tens digit
Number is 2x*10+x
Sum of digits is 2x+x=12
==>3x=12
==>x=4
Number is 84

Answer 2

Let x = the ones digit
Let y = the tens digit

x+2y=12
x=2y
x+y=12 substitute x for 2y to get:
(2y)+y=12 add like terms to get:
3y=12
3y=12 divide both sides by 3 to get:
y=4
x+y=12 substitute y for 4 to get:
x+4=12 subtract 4 from both sides to get:
x=8
so if x=ones
and y=tens
then the answer is 48