Answer
26.5 mL
Work Step by Step
$V_{1}=25.0\,mL$
$T_{1}=(20+273)K= 293\,K$
$T_{2}= (37+273)K=310\,K$
According to Charles's law,
$\frac{V_{1}}{T_{1}}=\frac{V_{2}}{T_{2}}$ (unchanging P and n)
$\implies V_{2}=\frac{V_{1}T_{2}}{T_{1}}=\frac{25.0\,mL\times310\,K}{293\,K}$
$=26.5\,mL$
