"12" in Engpsh is pronounced as "twelve."
The origin of this pronunciation comes from the Old Engpsh word "twelf," which is a combination of the words "two" and "left," as it was the 12th number counting from the left after the number 11.
Example sentences:
"I have twelve apples." (我有12个苹果。)
"The clock says twelve o'clock." (钟点是12点。)
"My birthday is on the twelfth of December." (我的生日在12月12日。)