Question

A scientist has 2/3 of liter of solution. He uses 1/2 of the solution of the solution for an experiment.

Answer 1

Remember,
To subtract 2/3-1/2 you have to make them equivalent
2/3×2-1/2×3 = 4/6 - 3/6=
1/6

Answer 2

You just have to multiplied :)

$\frac{1}{2} * \frac{2}{3} = \frac{1*2}{2*3} = \frac{2}{6} = \frac{1*2}{3*2} = \frac{1}{3}$

In short, the final answers : $\frac{1}{3}$ and $\frac{2}{6}$
Both answers are equivalent to each other

Hope this helps !

Photon