What is the result of adding these two equations?
5x−9y = 1
−7x+2y= -5

What is the 12th term of b(n)=-4-2(n-1)

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?

Olga bought a new skirt that cost $20. sales tax is 5%. how much did olga pay, including sales tax? 7.