a+b=84
b=a+3si1/5
b=a+3·5+1/5 ( 3·5+1 , totul supra 5)
b=a+16/5
a+a+16/5=84
2·a+16/5=84
2·a=84-16/5
aducem la acelasi numitor amplificam 84/1 cu 5
2·a=420/5-16/5
a=404/5:2
a=404/10 , simplificam cu 2 ⇒a = 202/5
b=202/5+16/5
b=218/5
PROBA : 202/5+218/5=420/5 , SIMPLIFICAM CU 5 ⇒ 84