The correct answer is 9.76 :)
well, do a payments table of values, just like before for each mont hmm let's see
1st month.......................3500 + p(1)
2nd month....................3500 + p(2)
3rd month.....................3500 + p(3)
4th month.....................3500 + p(4)
5th month.....................3500 + p(5)
36th month..................3500 + p(36)

Isolate the variable by dividing each side by factors that don't contain the variable.
-6x-15+15=4x+35+15
-6x=4x+50
(Subtract 4 on both sides)
-10x=50
(Divide by 10 on both sides)
x=5
I believe the answer is 375