Question 190869
When the digits of a two-digits number are reversed, the new number is 36 more
 than the original number. The units digits is twice the tens digit.
 What is the original number?
:
Let x = original 10's digit
Let y = original units
10x + y = original number
:
"When the digits of a two-digits number are reversed, the new number is 36 more than the original number."
10y + x = 10x + y + 36
10y - y = 10x - x = 36
9y = 9x + 36
Simplify divide by 9
y = x + 4
:
" The units digits is twice the tens digit."
y = 2x
:
Substitute;
2x = x + 4
x = 4, then y = 8
;
 What is the original number?   It's 48
;
;
Check solution 84 = 48 + 36