Answer: The correct option is
(C) subtract one x block from the left side and subtract two numbered blocks from the right side
Step-by-step explanation: Given that the balanced scale represents the following equation:

One x block is subtracted from the right side and two numbered blocks are subtracted from the left side.
We are to select the correct process that will balance the scale.
If we subtract one x block from the right side and two numbered blocks are subtracted from the left side, then equation (i) becomes

Now, to balance the scale, we must subtract one x block from the left and two numbered blocks from the right.
That is,
equation (ii) becomes

which is same as the balanced equation (i).
Therefore, we required process is to subtract one x block from the left side and subtract two numbered blocks from the right side.
Thus, the correct option is (C).