To find the combined water capacity of the two water towers, we need to add the capacities of the two towers.
The capacity of the first tower is \( 7.35x \) gallons, and the capacity of the second tower is \( 9.78x \) gallons.
So, we add the two capacities together:
\[ 7.35x + 9.78x = (7.35 + 9.78)x = 17.13x \]
Now, we need to express the result in standard form.
The combined water capacity is \( 17.13x \) gallons.
However, the options provided indicate that the answer may be formatted in scientific notation. Therefore, we should express 17.13 in scientific notation:
\[ 17.13 = 1.713 \times 10^1 \]
Thus, the combined capacity in scientific notation becomes:
\[ 17.13x = 1.713 \times 10^1 x \]
It is important to combine the \( x \) notation correctly. The resulting answer isn't provided directly in your choices, as they all seem to have the "x" together with the powers of 10 as separate elements (like \( 1.713 \times 1.713 \times 10^x \)), which doesn't align.
After reviewing the options, the best match for \( 17.13x \) in a simplified form is:
- None of the given choices represent \( 17.13x \) directly in a standard form. However, if you're looking just for a straightforward presentation, the capacity \( 1.713 \times 10^5 \) (choice E) seems like a misrepresentation since the combined \( x \) doesn't change the exponent of 10.
Thus, if you meant compound operations or \( 1.713 \) adjustments, then technically E is the nearest reasonable estimate without clearer notation in your provided choices.
So, since \( 17.13x \) is what we derived, it would match best with Option E: \( 1.713 \times 10^5 \), assuming here \( x \) must be correctly counted. Otherwise, choices seem unclear.