a - nr de probleme rezolvate in prima zi
b- nr de probleme rezolvate in a doua zi
a + b = 20
a = 3b
3b + b = 20 => 4b = 20 => b = 5
a = 3 × 5 => a = 15
sau
1. Cate probleme a rezolvat in a doua zi ?
20 : 4 = 5
2. Cate probleme a rezolvat in prima zi ?
3 x 5 = 15
