could not understand why in (2) The number of employees who ate only salads was equal to the number who ate both sandwiches and salads.
Official Solution: At a certain company event, the snack table offered only sandwiches and salads. If 300 employees attended the event and 180 employees ate sandwiches, how many employees ate neither sandwiches nor salads? {Total} = {Sandwiches} + {Salads} - {Both} + {Neither}
300 = 180 + {Salads} - {Both} + {Neither}
{Neither} = ?
(1) The number of employees who ate salads was equal to the number who ate neither sandwiches nor salads.
This implies {Salads} = {Neither}.
Substituting into the main equation:
300 = 180 + {Neither} - {Both} + {Neither}
300 = 180 + 2{Neither} - {Both}
We have two unknowns ({Neither} and {Both}). Cannot solve. Not sufficient.
(2) The number of employees who ate only salads was equal to the number who ate both sandwiches and salads.
This implies {Salads} - {Both} = {Both}, thus {Salads} = 2{Both}.
Substituting into the main equation:
300 = 180 + 2{Both} - {Both} + {Neither}
300 = 180 + {Both} + {Neither}
Again, two unknowns ({Both} and {Neither}). Cannot solve. Not sufficient.
(1)+(2) From (1), we have 300 = 180 + 2{Neither} - {Both}. From (2), we have 300 = 180 + {Both} + {Neither}. Thus, we have two distinct linear equations with two unknowns ({Neither} and {Both}), and we can solve for {Neither}. Sufficient.
Answer: C