Which expressions are equivalent to (x^2 - 9) (x+3) select the equivalent expressions ( 3 answers please)
A) (x+3)^2 (x-3)
B) x-3)^2 (x+3)
C) (x+3)^3
D) (x+3) (x+3) (x-3)
E) (x+3) (x-3) (x-3)
F) [(x)^2 + (3)^2} (x-3)

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?