Let x represent that number
x²=49
Square root for each side
√(x²)=√(49)
x=7
x³=343
Cube root for each side
³√(x³)=³√(343)
x=7
Check:
When 7 is square, it answer is 49.
When 7 is cubed, the answer is 7*7*7=343. As a result, the correct answer is 7. Hope it help!