Sabrina has 12 spools of ribbon. Each spool has either 3 yards of ribbon,
5 yards of ribbon, or 8 yards of ribbon. If
Sabrina has a total of 68 yards of
ribbon, how many spools of each length
of ribbon does she have?

How do you find the area of this triangle.

How do i do this? i don’t understand

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?