What is the variable in this expression 12/w+3

Ivan and jeff buy a package of 8 pens for $4.00. ivan wants 5 of the pens, and jeff wants 3.how much should each student pay?

36x2 + 49y2 = 1,764 the foci are located at: (-√13, 0) and (√13,0) (0, -√13) and (0,√13) (-1, 0) and (1, 0)edit: the answer is (- the square root of 13, 0) and (the square root of 13, 0)

Vinny is interviewing for a job.he wants his take home pay to be at least $42,000.what is the least salary he can earn if he pays 25% income tax?