Question

4 pixuri si 15 caiete...53 lei
4 pixuri si 10 caiete ...38 lei 
Cit costa un pix si cit un caiet?

Answer 1

$\left \{ {{4p+15c=53} \atop {4p+10c=38}} \right.$
$\left \{ {{4p+15c=53} \atop {-4p-10c=-38}} \right.$
Le aduni
$4p-4p+15c-10c=53-38$
$5c=15$
$c=3$
$4p+45=53$
$4p=53-45$
$4p=8$
$p=2$