Răspuns :
cel mai simplu
aplici produs mezi=produs extremi
25a-10b=12a+4b
25a-12a=10b+4b
13a=14b | impartim prin b
13a/b=14 |im[partim prin 13
a/b=14/13
altfel
impartim toata relatia cu b
(5a/b-2)/(3a/b+1)=4/5
25a/b-10=12a/b+4
13* (a/b)=10+4=14
a/b=14/13
asta a fost mai complicata, am facut-o pt.verificare
[tex] \\ \\ \dfrac {5a-2b}{3a+b}= \dfrac {4}{5} \iff 5(5a-2b) = 4(3a+b) \\ \\ \\
5(5a-2b) = 4(3a+b) \iff \\ \\
25a-10b =12a+4b \iff \\ \\
25a-12a=10b+4b \iff \\ \\
13a=14b \Rightarrow \boxed{\boxed{\dfrac{a}{b}=\dfrac{14}{13}}} \\ \\
[/tex]