You are buying boxes of cookies at a bakery. Each box of cookies costs 4$. In the equation below, c represents the number of boxes of cookies you buy, and d represents the amount the cookies will cost you (in dollars).
The relationship between these two variables can be expressed by the following equation:
d=4c
Identify the dependent and independent variables.

The number of boxes of cookies you buy
The amount the cookies will cost in dollars

Each person in an it department of 25 people works on at least one of 3 major projects: system security, program implementation, platform development. 10 people work on system security, 13 work on program implementation, and 12 work on platform development. 4 people work on system security and platform development, 5 people work on program implementation and platform development, and 2 people work on all three projects. how many people work on system security and program implementation?