Question

La un concurs de mate se acorda 5 pct pt o prob rezolvata corect si se scad 2 pct pt o prob gresita.Alexandru a trimis 20 prob rezolvate si a prinit 72 puncte .
Cate prob a rezolvat bine si cate gresit?

Answer 1

a=probleme rezolvate corect
b=probleme gresite
5a -2b=72
a+b=20
a=20-b
5(20-b)-2b=72
100-5b-2b=72
7b=28
b=4 probleme gresite
a=20-4=16 probleme corect rezolvate

Answer 2

x=probleme rezolvate corect

y=probleme rezolvate greșit

5x-2y=72

x+y=20

x=20-y

5*20-y-2x=72

100-5y-2x=72

7y=28⇒y=28:7⇒y=4(probleme rezolvate greșit)

x=20-4=16(probleme rezolvate corect)