Karin is also in Mr. Whittaker’s science class, and she recorded the variation in water level at a different part of the river. Karin observed that the water level there fell 1.68 millimeters per year for 1.5 years. Which expression shows a way to use the distributive property to solve for the total variation in water level at this part of the river? 1.5(-1) + 0.68 1 + (0.5)(-1)(0.68) (-1.68)(1) + (-1.68)(0.5) 1(-1) + 0.5(-0.68)

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?