Add 7.3 x 10 ^7 + 1.8 x 10^7 which is the correct sun

To add the numbers \( 7.3 \times 10^7 \) and \( 1.8 \times 10^7 \), you can first combine their coefficients, since they have the same exponent.

\[
7.3 + 1.8 = 9.1
\]

Now, keeping the common exponent of \( 10^7 \), you get:

\[
9.1 \times 10^7
\]

So, the sum of \( 7.3 \times 10^7 + 1.8 \times 10^7 \) is:

\[
9.1 \times 10^7
\]