Question

Maria a cumparat opt creioane si sase caiete si a platit 20 de lei.prietena ei ioama a cumparat 4 creioane si 6 caiete si a platit 16 lei .cat costa un creion?

Answer 1

a=creioane; b=caiete
8a+6b=20
4a+6b=16=>4a=16-6b
2 (16-6b)+6b=20
32-12b+6b=20
32-20=6b
12=6b=>12:6=b=>2=b

8a+6b=20
8a+6×2=20
8a+12=20=>8a=20-12
8a=8=>a=1

8×1+6×2=20
8+12=20
20=20

4×1+6×2=16
4+12=16
16=16