$\{\begin{array}{l}0,04x+0,025y=0,034\cdot 3,75|\cdot 100\\ x+y=3,75\end{array}$

$\{\begin{array}{l}4x+2,5y=3,4\cdot 3,75\\ x+y=3,75\end{array}$

$\{\begin{array}{l}4x+2,5y=12,75\\ x=3,75-y\end{array}$

$4\cdot \left(3,75-y\right)+2,5y=12,75$

$15-4y+2,5y=12,75$

$-1,5y=-2,25|:(-1,5)$

$y=1,5$

$\{\begin{array}{l}y=1,5\\ x=3,75-1,5\end{array}$

$\{\begin{array}{l}x=2,25\\ y=1,5\end{array}$

Użyto $2,25\mathrm{kg}$ solanki o stężeniu $4\%$.

$2,25\mathrm{kg}=2250\text{g}$