For this case we have that David drew the cards given by:
We have:
Where "x" represents the sum of the cards that David drew.
To add, we first group similar terms:
Taking into account that equal signs are added and the same sign is placed, we have:
Taking into account that different signs are subtracted and the sign of the major is placed, we have:
Thus, the sum of David's three cards is
Answer:
The sum of David's three cards is 2