If one number is thrice the other and their sum is $16$, find the numbers If one number is thrice the other and their sum is $16$, find the numbers.
I tried, 
Let the first number be $x$ and the second number be $y$
Acc. to question  
$$
\begin{align}
x&=3y &\iff x-3y=0 &&(1)\\
x&=16-3y&&&(2)
\end{align}
$$

Let the 1st number be $x$ and the 2nd number be $3x$. Since $x + 3x = 16$, $4x = 16$, so $x=4$. Therefore, 1st number is $4$ and the other is $12$.   
