Răspuns:
Explicație pas cu pas:
a/b = 2/7 rezulta a = 2b/7
3a + 2b = 6b/7 + 2b = 6b/7 + 14b/7 = 20b/7
5a - b = 10b/7 - b = 10b/7 - 7b/7 = 3b/7
(3a + 2b)/(5a - b) = 10b/7 : 3b/7 = 10b/7 * 7/3b = 10/3
a/b=2/7=>b=7a/2
(3a+2·7a/2 ) / (5a-7a/2)=
10a/(10a/2-7a/2)=
10a:(3a/2 )=10a·2/3a=20/3
