Answer:
4
Step-by-step explanation:
Let the number to be added be represented by x. Then we want ...
[tex]\dfrac{11+x}{37+2x}=\dfrac{1}{3}\\\\3(11+x)=37+2x\\\\3x+33=2x+37 \quad\text{simplify}\\\\x=4 \quad\text{subtract $2x+33$}[/tex]
The number is 4.