Question

the sum of the digits of two-digit number is 6 if the digit at units place is twice the digit at tens place then the number was

Answer 1

Let the one's digit place be = x
&
Let the tens place digit be = y
A.T.Q.
X+y=6 ...1
&
2x = y. ....2
Put y=2x in eq 1
I.e.
2x+x=6
3x=6
X=2
Now find the value of y by subsiducing method

Answer 2

Let number is xy
so ones digit is y and tens digit is x
since x+y=6

Since second condition
y = 2x

So using this
x+2x=6
3x=6
x=2

Since y = 2x
so y = 2×2 =4
So ones digit is 4 and tens digit is 2

So number is 24