If John gave his fiancee a $4000 ring on their engagement day, a $2000 car as a gift on their wedding day, the total cost for the two presents is $4000+$2000=$<<4000+2000=6000>>6000.
He also gave his fiancee a diamond brace twice as expensive as the ring costing 2*$4000=$<<2*4000=8000>>8000
The total worth of the presents John gave to his fiancee is $6000+$8000 =$<<6000+8000=14000>>14000
#### 14000