Question

Un bloc are 190 camere , in care are 60 de apartamente. Sunt apartamente 2 camere si 4 camere. Aflati cate camere sunt de 2 camere si 4 camere. Va multumecs ca ma ajutati

Answer 1

notam
x ap cu 2 camere
y ap cu 4 camera,
atunci avem  
2*x+4*y=190 camere
dar mai stim x+y=60
x=60-y

inlocium in prima relatie  si avem

2*(60-y)+4y=190
120-2y+4y=190
120+2y=190
2y=190-120=70
y=70:2=35 ap cu 4 camere
x=60-35=25 ap cu 2 camere

proba 
2*25=50 camere
4*35=140 camere
50+140=190 camera ( atat cat a spusproblema )

Succes !

Answer 2

$x-nr. \ de \ apartamente \ cu \ 2 \ camere \\ y-nr. \ de \ apartamente \ cu \ 4 \ camere \\\\ \left \{ {{x+y=60} \ |(-2) \atop {2x+4y=190}} \right. \\\\ \left \{ {{-2x-2y=-120} \atop {2x+4y=190}} \right. \\ ========= \\\\ 2y=70 \ |:2 \\\\ \boxed{y=35} \\\\ x+y=60 \\\\ x=60-y \\\\ x=60-35 \\\\ \boxed{x=25}$