Replace 2 tires or 4?

We got a screw in one of our tires and it is not repairable. The car has 21,000 miles and the original tires have between 5/32 and 6/32 of tread left. Should I replace just the two rear tires? Or at this point is the tread wear enough that I should just get all 4? This is a 2007 2WD, Rav4.

Thanks

hello,if there is 5-6/32 left i'd just replace the 1 or 2.if you replace the 2 you might want to keep the best for the spare.(if it's a full size)Good Luck

Thanks. I've already got a good full-size spare, so I think I am going to replace two tires with a different brand - same size, rating, etc.