7 stilouri+6 pixuri=235 lei
2 stilouri+3 pixuri= 80 lei
9 s+9 p=235+80
9(s+p)=315
s+p=315:9
1s+1p=35
2s+3p=2(s+p)+p=80
2x35+p=80
70+p=80
p=80-70
p=10 lei costa un pix
7 s+6x10=235
7 s+60=235
7 s=235-60
7 s=175
s=175:7
s=25 lei costa 1 stilou
V: 7x25+6x10=175+60=235
2x25+3x10=50+30=80