1. If we set b to the number of total brothers, and s to the total number of sisters, we can write and solve the following system:

b - 1 = s (because the number of total brothers, minus Simon is equal to the number of sisters)

2(s - 1) = b (because twice the number of sisters, minus Sophia is equal to the number of brothers)

Solving for this gives us a total of 4 brothers and 3 sisters, meaning there are 7 total children (assuming all the brothers and sisters are children)

hope this helps (sorry if it took too long)