Kenny and Ben start competing businesses selling hats. Kenny buys supplies, costing $3, before he starts selling his hats for $0.50 each. Ben sells his hats for $0.25 each and spent only $1 on supplies. At
what point have they sold the same number of hats and made the
same profit (income minus costs)?

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?