An employee earns a 25% commission rate on his sales. One day, he earned $175. What was his amount of sales?

Evaluate the expression for the given value of the variable 7a - 4a for a =8

Which of these tools or constructions is used to inscribe a hexagon inside a circle?

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?