Which symbol replaced the unit of atomic mass,$amu$?

An alloy of metals $X$ and $Y$ weighs $12 \ g$ and contains atoms $X$ and $Y$ in the ratio of $2:5$. The percentage of metal $X$ in the alloy is $20$ by mass. If the atomic mass of $X$ is $40$,what is the atomic mass of metal $Y$ (in $amu$)?

$1 \ amu$ is equal to

The equivalent weight of a bivalent metal is $37.2$. The molecular weight of its chloride is

The atomic mass of a metal is $27$ and its equivalent mass is $9$. What is the formula of its chloride?

$1 \, g$ of hydrogen combines with $80 \, g$ of bromine,and $1 \, g$ of calcium combines with $4 \, g$ of bromine. What is the equivalent weight of calcium?