$\left(6.8 \times 10^{3}\right)+\left(2.6 \times 10^{5}\right)$

Step 1 ：The problem is asking to add \(6.8 \times 10^{3}\) and \(2.6 \times 10^{5}\).

Step 2 ：Since the exponents are different, we cannot directly add the numbers. We need to convert them to the same base exponent.

Step 3 ：The larger exponent is \(10^{5}\), so we will convert \(6.8 \times 10^{3}\) to the base of \(10^{5}\).

Step 4 ：To do this, we move the decimal point in 6.8 two places to the left, giving us 0.068.

Step 5 ：Now we can add the numbers: \(0.068 + 2.6 = 2.668\).

Step 6 ：Finally, we convert back to the original form by moving the decimal point in 2.668 five places to the right, giving us 266800.0.

Step 7 ：Final Answer: \(\boxed{266800.0}\)