-18-6k=6(1+3k)...what is the value of k

Bonnie and bobby are saving money for a vacation. each friend starts with an amount and also saves a specific amount each week. bonnie created a table to show the total she has saved at the end of each week.. weeks 0 1 2 3 4 5 6 7 8 amount saved 12 16 20 24 28 32 36 40 44 bobby came up with the following equation to show the total, y, he has saved at the end of each week, x. y = 12x + 4 compare the rate at which each friend saves money. select the correct answer from the drop-down menu to complete the statement. the rate at which bobby is adding to his savings each week is $ more than the rate at which bonnie is adding to her savings each week.

Can someone me with this? i’m not sure what to put for my equations.

What is the sum of the geometric series in which a1 = 7, r = 3, and an = 1,701? hint: cap s sub n equals start fraction a sub one left parenthesis one minus r to the power of n end power right parenthesis over one minus r end fraction comma r ≠ 1, where a1 is the first term and r is the common ratio