The singleshot Stevens 15A and 15B .22 rifles are worth %50 to $150, depending on the condition. The higher-end price seems to keep them sitting around for quite a while.
I can't say for certain the age of the Stevens 15B but I can tell you I bought mine brand new between 1962 and 1965. I was a young lad so it's hard to remember. If I recall correctly, I paid between $25 to $30 for it. I still have it and it is one of the most fun rifles I have owned.
I am not sure, but I hope at least $75 dollars because that is what I paid for one today. Fair condition at best. Brought it home and shot it and was not extremly impressed.
Minimal value of $40-$125 US depending on the condition.
Re-ordering it : 13a - a -15b + 2b = 12a - 13b
10ab + 15b = 5b (2a + 3)
15b+2-13 = 13b+6-4b 15b-11 = 9b+6 15b-9b = 6+11 6b = 17 b =17/6 or 2 and 5/6
3 x 5 x b = 15b No exponents required.
15b/39b4 = 5/13*b-3
15b + 13c - 12b + 10c + 8 = 3b + 23c + 8