Răspuns :
a+b=54 =>a=54-b
a=4(b-a) =>a=4b-4a => 5a=4b
=>5(54-b)=4b
270-5b=4b
270=9b
b=30
a=54-30=24
a=4(b-a) =>a=4b-4a => 5a=4b
=>5(54-b)=4b
270-5b=4b
270=9b
b=30
a=54-30=24
a+b=54
b=4×(a-b)⇒b=4a-4b⇒b+4b=4a⇒5b=4a⇒b=4a/5
a+4a/5=54 aducem la acelasi numitor
5a/5+4a/5=54
9a/5=54⇒9a=54×5⇔9a=270⇒a=270/9⇒a=30
a+b=54 si a=30⇒30+b=54⇒b=54-30⇒b=24
acum vedem ca b<a. sa vedem daca verifica conditia impusa in problema
24=4×(a-b)?
24=4×(30-24)
24=4×6
24=24 adevarat