Răspunsuri

2014-07-29T20:00:13+03:00
F+b=28

f=40% din b= 40/100*b= 10/25 *b= 2/5 *b=  2b/5

2b/5 +b=28 aducem la acelasi numitor

2b+5b=28*5

7b=28*5

b=28*5/7

b=4*5=20

f=28-20=8 
1 5 1
2014-07-30T00:00:43+03:00
F+b=28
f=40/100*b=2/5*b
Notez 1/5*b cu x ⇒ f=2x  si b=5x
2x+5x=28
7x=28
x=28:7=4 ⇒ f=2*4=8 si b=5*4=20