(2x+5y)/(x+y)=4,5
2x+5y=4,5x+4,5y
2,5x=0,5y
5x=y
x/y=1/5
5x/2y=y/2y=1/2
(x²+y²)/y²=(x²/y²)+1=(x/y)²+1=(1/5)²+1=1/25+1=26/25
8
a/3=b/4=c/7 b=4a/3 c=7a/3
a+b+c=70
a+4a/3+7a/3=70
3a+4a+7a=210
14a=210
a=15
b=4×15/3=20
c=7×15/3=35
procentul=a/b=15/20=0,75=75%
a reprezinta 75% din b
