Salut!
Răspuns: a ✔
a : b = 2 ==> a = 2b
b : c = 3 ==> b = 3c
a + c = 210
✏Rezolvarea:
a = 2b
b = 3c ==> a = 2 · 3c
a = 6c
6c + c =210
7c = 210
c = 210 : 7
c = 30 ✅
a = 6 · 30
a = 180 ✅
b = 3 · 30
b = 90 ✅
✒ a - b - c = 180 - 90 - 30
= 90 - 30
= 60 ✔
===> Răspuns corect a) 30 ✔