How do you even do this???

Find an bif a = {3, 6, 9, 12) and b = {2, 4, 6, 8, 10).

Sole the equation 6n + 9 = -3n - 21 - 6 for n

Jared had 3/7 of the minutes on a family phone plan remaining for the month. the plan is shared by 2 people. if divided equally what portion of the minutes remaining on the phone plan would be avalible for each person