Final answer:
The symbol to fill in the blank is '>', as 2.96 is greater than 2.78.
Step-by-step explanation:
The question asks to fill in the blank with a mathematical symbol comparing the numbers 2.96 and 2.78. To solve this, we simply observe that 2.96 is greater than 2.78. Therefore, the appropriate symbol to put in the blank is ">" making the complete statement 2.96 > 2.78. This comparison is based on the basic concept of numerical order where numbers to the right on the number line are greater than those to the left.