Ma = (a+b+c) : 3 = 80
a+b+c = 80×3 = 240
a = 3b/4
a = c - 40 ==> c = a + 40 = 3b/4+40
inlocuim in a 2-a relatie in functie de b
3b/4 + b + 3b/4 + 40 = 240
3b/4 + b + 3b/4 = 200 |×4
3b + 4b + 3b = 800
10b = 800
b = 800 : 10
b = 80
a = 3×80/4 = 3×20 = 60
c = 60+40 = 100
Verificare:
(60+80+100) : 3 = 240 : 3 = 80