I have a String like 

```
str1 = "...abc-10-11-09?"

```

and I need to replace *the last* `"-09"`.
So that result will be like 

```
"...abc-10-11-2?"

```

I have try 

```
Regex.Replace(str1, @"([0-9]+)\?", "$1-2?"), 

```

but I became `"...abc-10-11-09-2?"`

Could someone help me please.
Thank you.