Question 573778
Let's use X and Y to mean the two positive numbers we're looking for.
The difference between these is 16, so let's assume X is the bigger number.
X - Y = 16


"One number" is 3 times the other.  Since we already said X is the bigger number, then 
X = 3Y


Now we can solve since we have everything we need.  :-)  Since we already have one equation for X, let's use substitution method.  We'll plug "X=3Y" into the first formula in place of X.  Then we can solve for Y first.
X - Y = 16
(3Y) - Y = 16  
simplifying:
2Y = 16
Divide by 2 on both sides:
Y = 8
Since X is 3Y, 
X = 3(8) 
X = 24


Checking the first equation:
X - Y = 16
24 - 8 = 16
16 = 16  Correct!