Answer:
[tex]x+\frac{1}{3}x[/tex]
Step-by-step explanation:
a number plus is the following
let's say that the number is x
so we have
[tex]x+\cdots[/tex]
1/3 of the number
the number is x so it's 1/3 of x
[tex]\frac{1}{3}x[/tex]
add both expressions
[tex]x+\frac{1}{3}x\\\\[/tex]
