1/3 a number increased by 10 times by that same number

1/3 a number increased by 10 times by that same number

The phrase a number means an arbitrary variable, let's call it x.

1/3 a number
1/3 * x = x/3

That same number means the same arbitrary variable as above:
x

10 times that same number:
10x

The phrase increased by means we add:
x/3 + 10x