Question

Cunoscand ca a/b=3/7 calculati valoarea expresiei 5a-b/2a+3b
Urgent !!!

Answer 1

a/b=3/7
7a=3b
a=3b/7
(5a-b)/(2a+3b)=(15b/7-b)/(6b/7+3b)=[(15b-7b)/7]/[(6b+21b)/7]=
=8b/7]/27b/7]=[8b/7]x[7/27b]=8/27

Answer 2

7a=3b⇒a=3b/7;
⇒5a-b/2a+3b
⇒5·3b/7-b/2·3b/7+3b
⇒15b/7-b/6b/7+3b
⇒15b/7-7b/7/6b/7+21b/7
⇒8b/7/27b/7
⇒8b/7·7/27b
⇒8/7·7/27
⇒8/1·1/27
⇒8/27;