For 3 x 234, you could use the "groups of" meaning of X to make 3 groups of 234 as follows:
After making the 3 groups of 234, add (trading as needed). The result is 702.

Note that the following trading was needed:
10 1
10 1
For 268 2, first build 268:
Then split 268 into two equal groups. Each group would be:
The result is 134.