Final answer:
The total volume of all the tanks at the aquarium after the new dolphin tank is installed will be $3.0\times10^6$ gallons.
Step-by-step explanation:
To find the total volume of all the tanks at the aquarium after the new dolphin tank is installed, we need to add the volume of the new dolphin tank to the current combined volume of all the tanks.
Given that the combined volume of all the tanks is $2.65\times10^6$ gallons and the volume of the new dolphin tank is 350,000 gallons, we can calculate the total volume as follows:
Total volume = Combined volume + Volume of new dolphin tank
Total volume = $2.65\times10^6$ gallons + 350,000 gallons
Total volume = $3.0\times10^6$ gallons
Therefore, the total volume of all the tanks at the aquarium after the new dolphin tank is installed will be $3.0\times10^6$ gallons.