2. (3 points) A team of 8 people completed $\frac{1}{3}$ of a project in 30 days. Then, 4 more people were added to complete the remaining part of the project. How many days in total were used to complete the project?
【Analysis】Regarding this project as a unit "1", use “$\frac{1}{3} \div 30 \div 8=\frac{1}{720}$” to find the work efficiency of 1 person in 1 day, then the combined work efficiency of 12 people is $\frac{1}{720} \times 12=\frac{1}{60}$. Calculate the remaining work volume, and then use "work volume ÷ work efficiency = work time" to find the time used later, and thus the total time used to complete this project.
【Solution】Solution: The work efficiency of one person is $\frac{1}{3} \div 30 \div 8=\frac{1}{720}$,
The combined work efficiency of 12 people is $\frac{1}{720} \times 12=\frac{1}{60}$,
Total time required: $\left(1-\frac{1}{3}\right) \div \frac{1}{60}+30$
$=40+30$
$=70$ (days)
Answer: A total of 70 days were used.
Therefore, the answer is: 70.