A right triangle has a side length of 16 meters and hypotenuse of 20 meters.
Which equation can be used to find the missing leg in the triangle?
a2 + 202 = 162
202 + 162 = a2
a2 + 162 =202
16 + a2 = 20

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?