Răspuns :
a+b=21
a:b=4 rest 1=> a=4*b+1=> a=4b+1
4b+1+b=21=>5b=21-1=>5b=20=>b=20:5=>b=4
a=4*4+1=>a=17
a:b=4 rest 1=> a=4*b+1=> a=4b+1
4b+1+b=21=>5b=21-1=>5b=20=>b=20:5=>b=4
a=4*4+1=>a=17