What is the solution set of x^2-10=30x

When using the linear combination metho e linear combination method to solve a system of linear equations, the four options are:

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?

Traffic on saturday, it took ms. torres 24 minutes to drive 20 miles from her home to her office. during friday's rush hour, it took 75 minutes to drive the same distance. a. what was ms. torres's average speed in miles per hour on saturday? b. what was her average speed in miles per hour on friday?