Which instrument is used to measure the atomic mass of an atom accurately?

Which phrase would be incorrect to use?

In a copper sulfate solution,$3.2 \ g$ of copper is displaced by $2.8 \ g$ of iron. If the equivalent mass of iron is $28$,what is the equivalent mass of copper?

One atomic mass unit $(amu)$ is equal to:

Equivalent weights of $X_2Y$ and $X_2Y_3$ are $38$ and $18$ respectively. Find the atomic masses of $X$ and $Y$:-

Assuming chlorine element has two isotopes as $Cl^{35}$ and $Cl^{37}$ with their percentage abundance as $25\%$ and $75\%$ respectively. Find the average atomic weight.