Quick tube question

I need to change tube today. The original one is 26 x 1.9/2.125 and the one I got from the bike shop is 26 x 1.25-1-75.
Can I use that one or will the size be too small?

What size is the tyre?

Ok,thanks. I put the tube in and it works fine. I followed an advice from bicycletutor.co.