Answer: A. 20
Explanation:
For the general equation of ellipse :-
![((x-h)^2)/(a^2)+((y-k)^2)/(b^2)=1](https://img.qammunity.org/2020/formulas/mathematics/high-school/g67jy3q8dsudxo8pwn5ltqwrv1dbcbsmw4.png)
If a > b , then the length of major axis = 2a
If b> a , then the length of major axis = 2b
The given equation :
![((x-3)^2)/(49)+((y+6)^2)/(100)=1](https://img.qammunity.org/2020/formulas/mathematics/high-school/yjd9n0rb3hmqst37roijbxtwv3z9ywz1ep.png)
Which can be written as :
![((x-3)^2)/(7^2)+((y+6)^2)/(10^2)=1](https://img.qammunity.org/2020/formulas/mathematics/high-school/jzgm0obf4ffaxs758343k1151t4d2e58m2.png)
Here 10 >7 , then the length of major axis =2(10)=20 units