3.7 x 10^5 + 3.7 x 10^5

To add \(3.7 \times 10^5\) and \(3.7 \times 10^5\), you combine the coefficients since they have the same exponent.

\[ 3.7 + 3.7 = 7.4 \]

So, the sum can be expressed as:

\[ 7.4 \times 10^5 \]

Thus, \(3.7 \times 10^5 + 3.7 \times 10^5 = 7.4 \times 10^5\).