correct answer is: c) 300 & 420

Explanation

Two numbers ratio is 5 : 7
Let, One number is 5x
Another number is 7x
According to the question,
\left(5x+7x\right)=720
\rightarrow\ 12x\ =\ 720
\rightarrow\ x\ =\ \frac{720}{12}
\therefore\ x\ =\ 60
\therefore One number is ‘5x’ or \left(5\times60\right)
\rightarrow\ 300
And another number is ‘7x’ or \left(7\times60\right)
\rightarrow420
Ans: The numbers are 300 & 420.