Let's use the variables x and y to represent the numbers.
If the sum is equal to 36, we have:
[tex]x+y=36[/tex]If one number is 3 times as large as the other, we have:
[tex]x=3y[/tex]Using this value of x in the first equation, we have:
[tex]\begin{gathered} (3y)+y=36 \\ 4y=36 \\ y=\frac{36}{4} \\ y=9 \\ \\ x=3y=3\cdot9=27 \end{gathered}[/tex]Therefore the larger number is 27 and the smaller number is 9.