Given:

V\(_1\) = 30cm\(^3\)

T\(_1\) = 50\(^0\)C + 273 = 323K

V\(_2\) = ?

T\(_2\) = 80\(^0\)C + 273 = 353K

According to Charles' law:  \(\frac{V_1}{T_1}\) = \(\frac{V_2}{T_2}\)

 V\(_2\) = \(\frac{{353}\times{30}}{323}\)  

 V\(_2\) = 32.79 cm\(^3\)

Increase in volume =  V\(_2\) - V\(_1\) = 32.79 - 30 = 2.79 cm\(^3\)

Fractional increase in volume =  \(\frac{{V_2} - {V_1}}{V_1}\) 

  =  \(\frac{{32.79} - {30}}{30}\)

  = 0.09287

  = 0.093