Question 572221
Let's use X and Y to denote the two numbers we're looking for.

X + Y = 15
X = 4Y


Substitute the 4Y into the first equation for X gives us
(4Y) + Y = 15
5Y = 15  Divide both sides by 5
Y = 3.


One number is 3.


But we know 3 and the other number add to 15.  Therefore,
X + 3 = 15
X = 12

So the two numbers are 3 and 12.


Check:
3 + 12 = 15
AND
4 X 3 = 12  Correct!