Trying to understand multi thread

Makingt that must use multithread. (1) your main thread will ask user to input a number x. your main thread will create x number of new threads as workers and wait for the main thread to give them order to do the calculation. (2) your program needs to support multiple sessions: for each session, the main thread will ask user to input te desired precision of pi, then the main thread will ask worker thread to part of the calculation and combine the results from workers to computer pi. the calculation result should meet the desired precision. the maximum precision is 30 digit. (3) you will need to demonstrate your code and explain your code in the demo at the linux. your code should also be well-commented