Answer :
if you mean 1/2 times the square root of 343 then the answer is 1/3 times 7√7=(7/3)√7
if you means the cube root of 343 (because x^1/3=∛x), thenthe answer is 7
if you means the cube root of 343 (because x^1/3=∛x), thenthe answer is 7