Răspuns:
Explicație pas cu pas:
(a+3b)/(5a+b)=5/11 ⇔ 11(a+3b)=5(5a+b) ⇔ 11a+33b=25a+5b ⇔
33c-5b=25a-11a ⇔ 28b=14a ⇔ 2b=a
(2b+c)/(b+2c)=7/5 ⇔ 5(2b+c)=7(b+2c) ⇔ 10b+5c=7b+14c ⇔ 10b-7b=14c-5c ⇔ 3b=9c ⇔ b=3c
a) 50%·a=(50/100)·a=(1/2)·a=a/2
2b=a ⇔ b=a/2 ⇔ b=50% din a
b) b=a/2 |:a ⇔ b/a=(a/2)/a=(a/2)·(1/a)=a/2a=1/2 ⇒ b/a=1/2
b=3c ⇔ c=b/3 |:b ⇒ c/b=(b/3)/b=(b/3)·(1/b)=b/3b=1/3 ⇒ c/b=1/3
c) 2b=a
b=3c ⇔ c=b/3 ⇒
a+b+3c=36 ⇔ 2b+b+3·(b/3)=36 ⇔ 2b+b+b=36 ⇔ 4b=36 ⇔ b=9
a=2b=2·9=18 ⇔ a=18
c=b/3=9/3=3 ⇔ c=3
