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You think you're a really good boxer. Try step into the ring. I bet the next thing you know you passed out.

Is the above correct?
Thanks.
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New2grammarYou think you're a really good boxer. Try step into the ring. I bet the next thing you know you passed out.

Is the above correct?
Thanks.

Not quite.

"You think you're a really good boxer. Try stepping into the ring. I bet the next thing you know you'll pass out".
Comments  
Students: We have free audio pronunciation exercises.
How about "Try to step into the ring"?

How about "the next think you know is you passing out"?
New2grammarHow about "Try to step into the ring"? - OK

How about "the next think you know is you passing out"? Not for me.