x - znaczki dziadka
y - znaczki Jacka
\left \{ {{x-150=y+150} \atop {x-\frac{3}{4}x=y}} \right.
\left \{ {{x=y+150+150} \atop {x-\frac{3}{4}x=y}} \right.
\left \{ {{x=y+300} \atop {x-\frac{3}{4}x=y}} \right.
\left \{ {{x=y+300} \atop {y+300-\frac{3}{4}(y+300)=y}} \right.
\left \{ {{x=y+300} \atop {y+300-\frac{3}{4}y-\frac{3*300}{4}=y}} \right.
\left \{ {{x=y+300} \atop {y-y-\frac{3}{4}y+300-225=0}} \right.
\left \{ {{x=y+300} \atop {-\frac{3}{4}y+75=0}} \right.
\left \{ {{x=y+300} \atop {-\frac{3}{4}y=-75}} \right.
\left \{ {{x=y+300} \atop {y=-75:(-\frac{3}{4})}} \right.
\left \{ {{x=y+300} \atop {y=-75*(-\frac{4}{3})}} \right.
\left \{ {{x=y+300} \atop {y=100}} \right.
\left \{ {{x=100+300} \atop {y=100}} \right.
\left \{ {{x=400} \atop {y=100}} \right.
Dziadek ma 400, a Jacek 100 znaczków.