Julius has three times as many stamps in his collection as his friends Liam and Mario combined. Liam has 10 stamps in his collection. Julius has 87 stamps in his collection. How many stamps does Mario have in his collection?
The equation 3(x + 10) = 87 models this situation. Which choice shows the sequence of operations needed to solve this problem, using both arithmetic and algebra?

1. 87 - 10 = 77; 3x = 77; x = 77 ÷ 3
2. 3x + 10 = 87; 3x = 77; x = 77 ÷ 3
3. 3x = 87 - 10; x = 77 ÷ 3
4. x + 10 = 87 ÷ 3; 3x = 77; x = 77 ÷ 3
Answer: 3. 3x = 87 - 10; x = 77 ÷ 3