Just as a clarification, the word is "yoked." Unless you're talking about eggs.
A yoke is made of wood, has two holes in it for two animal heads to go through'; the yoke forces them to act as one. You would yoke two animals this way to pull a plow, for example. Animals needed to be of comparable strength and size when yoked, otherwise the slower animal would hold back the stronger one, or the slower animal will work itself to death trying to keep up with the stronger animal. So the idea is that the marriage will not work well because a non-Christian is too incompatible with a Christian.
In the next chapter, Paul lays out what Christians are to do if they are married to a non-Christian.
1 Cor. 7:12-14:
“…If any brother has a wife who is not a believer and she is willing to live with him, he must not divorce her. And if a woman has a husband who is not a believer and he is willing to live with her, she must not divorce him. For the unbelieving husband has been sanctified through his wife, and the unbelieving wife has been sanctified through her believing husband…”
vs. 15
"But if the unbeliever leaves, let him do so. A believing man or woman is not bound in such circumstances; God has called us to live in peace."
So Paul says that if the unbeliever in the pair is willing to stay with the believer, then they ought to remain married. Yet if the unbeliever wants to leave, he/she is free to go. In either case, it is the unbeliever who gets to make the decision; believers, it seems, are asked to make the marriage work as long as the unbeliever wants it to.