BMass of air does not remain constant
b
No, because the mols of air and also changing in this case as you blow into the balloon
we have,
$P V=n R T .$
Let the tempenatune stays constant when you blow in to a balloon, if $P$ increases by scale facton of $x$ and $V$ increases by scale facton of $x$, then the number of mols would have to increse by Scale facton of $x^{2}$.
$\frac{P V}{n}=R T .$
To express this realtionship:
$\frac{P_{1} V_{1}}{n_{1}}=\frac{P_{2} V_{2}}{n_{2}} .$