"Three times two equals six."
Translation:Tri lluosi dau yn hafal i chwech.
Not only with negatives - remember things such as Dw i'n hoffi coffi or Dych chi'n yfed te? Those have yn, in the shape of 'n.
With negatives that have ddim or dim, those end in a consonant and so yn stays yn, while in positive sentences, we've usually used pronouns which end in a vowel so it becomes 'n, but the yn is there just the same.