Teresa,
As Jean as previously stated use some wrapper from something like clif bars, power bars, etc and cut into a square big enough to cover the slash and then some. Pop your tube in and mount the tire back and inflate and you're back in business. If the tire separates too much at the slash when inflated you're better off with a new tire. Which tire was it BTW (front or back)?
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Litespeed, lasts a lifetime.
Specialized Tarmac, lasts a lifetime, or until it breaks.