Răspuns:
Explicație pas cu pas:
fie a,b, c, d cele patru numere
[tex]\it a+b+c+d=3989\\\\b=3\cdot a-20\\\\c=a:2+50\\\\d-30=2\cdot b\Rightarrow d=2b+30 \Rightarrow d=2\cdot3a-20\cdot2+30\Rightarrow d=6a-10\\\\inlocuim\: pe\:a,\:b,\:c\: in\:suma\\\\a+3a-20+a:2+50+6a-10=3989\\\\10a+20+a:2=3989\\\\2\cdot10a+2\cdot20+a=3989\cdot2\\\\20a+a+40=7978\\\\21a=7978-40\\\\21a=7938\\\\a=7938:21\Rightarrow\boxed{a =378}\\\\b=3\cdot378-20\Rightarrow b=1134-20\Rightarrow\boxed{b =1114}\\\\c=378:2+50\Rightarrow c=189+50\Rightarrow\boxed{c=239}\\\\d = 2\cdot1114+30\Rightarrow \boxed{d=2258}[/tex]
Verificare:
378 + 1114 + 239 + 2258 = 3989 (adevarat)
