I need help in finding out a formula that will help me in calculating the final prices of things and to give me a constant profit of 30.00.

Final price =X (unknown)
Transaction fees of final price .35 +13%
Shipping/handling + processing costs =31.06 I am charged this by company that send me the items.


Profits to be = to 30.00
Item costs for me = variable such as 34.00 or 83.00 which is a number than can be changed as costs change.

So
final price x 13% - .35 - my costs - ship/handling costs =30.00 profit

If I understand you correct:
x = final price
t = transaction fees
c = transaction/handling and processing costs
P = profit
then
x = t+c+p
x = 0.35 + 0.13x + 31.06 + 30.00
0.87x = 61.41
x = 70.59

Only thing is you forgot the cost of the items. Such as 84.00 cost to me to buy the item to have in stock.

So problem solved, or?