[tex]Cp=\frac{m_s}{m_r}*100\%\\
\\
Cp=20\%\\
m_{rozp.}=3kg=3000g\\
m_r=m_s+m_{rozp.}\\
\\
20\%=\frac{m_s}{m_s+3000g}*100\% /:100\%\\
\frac2{10}=\frac{m_s}{m_s+3000g}\\
\\
2(m_s+3000g)=10m_s\\
2m_s+6000g=10m_s /-2m_s\\
6000g=8m_s /:8\\
750g = m_s\\
\\
\text{Trzeba wsypac 750g cukru}[/tex]
