Tina makes 480 sandwiches.
She only makes tuna sandwiches, beef sandwiches, ham sandwiches and
cheese sandwiches.
of the sandwiches are tuna. 35% of the sandwiches are beef.
The ratio of the number of ham sandwiches to the
number of cheese sandwiches is 5:6
Work out the number of ham sandwiches that Tina makes.

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?