Question

In how many months will the total cost of both options be the same? What will that cost be?

Answer 1

If you make yourself a monthly expense chart:
                                                       Months
                      1       2            3           4        5        6       7      8        9        10
Opt 1         -80      -30        -30        -30      -30     -30    -30    -30   -30      -30
Opt 2         -40     -40        -40        -40       -40      -40    -40    -40    -40   -40

By month 5 the total amount spent for Opt 1 is $200 and Opt 2 is $200

For part two add up the values for each all the way up to month 9.
Option 1:   80 + 30(8) =  80 + 240 = 320 spent
Option 2:   40(9)  = 360  spent

So option 1 is cheaper by month 9