For thousands of years, gold has been considered one of the Earth's most precious metals. One hundred percent pure gold is 24-karat gold, which is too soft to be made into jewelry. Most gold jewelry is 14-karat gold, approximately 58% gold. If 18-karat gold is 75% gold and 12-karat gold is 50% gold,
how much of each should be used to make a 14-karat gold bracelet weighing 300 grams?
How many grams of 18-karat gold needs to be used to make the bracelet?

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?