[tex]C_p=\frac{m_s}{m_r}\cdot100\%\\\\C_p_1=25\%, \ m_r_1=240 \ g\\\\\frac{m_s_1}{240g}\cdot100\%=25\% \ \ |:100\%\\\\\frac{m_s_1}{240g}=0,25 \ \ |\cdot240 \ g\\\\m_s_1=60 \ g\\\\-----------\\\\m_s_2=60 \ g\\\\m_r_2=240 \ g+30 \ g=270 \ g\\\\C_p_2=\frac{60g}{270g}\cdot100\%\approx\boxed{22\%}[/tex]
