Resposta :
{[(21 ÷ 7 + 3 ÷ 1) + (2 + 4)] ÷ (2 × 6 ÷ 2 - 15)} × 3
{[(3 + 3) + 6] ÷ (1 × 6 - 15)} × 3
{[6 + 6] ÷ (6 - 15)} × 3
{12 ÷ (-9)} × 3
- 12/9 × 3
- 4/3 × 3
-4
{[(21 ÷ 7 + 3 ÷ 1) + (2 + 4)] ÷ (2 × 6 ÷ 2 - 15)} × 3
{[(3 + 3) + 6] ÷ (1 × 6 - 15)} × 3
{[6 + 6] ÷ (6 - 15)} × 3
{12 ÷ (-9)} × 3
- 12/9 × 3
- 4/3 × 3
-4