Step-by-step explanation:
The two like fractions can be set as x and y (just to use two variables).
One of them is [tex]\frac{3}{12}[/tex], though, so we can set one of the variables equal to that value (I'm just going to make [tex]y=\frac{3}{12}[/tex], it doesn't matter which variable you use).
We also know that adding the two variables gives us [tex]\frac{1}{3}[/tex] so now we can make an equation.
[tex]x+y=\frac{1}{3} \\x+\frac{3}{12} =\frac{1}{3} \\x=\frac{1}{3} -\frac{3}{12} \\x=\frac{4}{12} -\frac{3}{12} \\x=\frac{1}{12}[/tex]
Answer:
[tex]\frac{1}{12}[/tex]