Dhaval Rabadia: Your Trusted Tutor and Mentor

Answer

In our day to day life, we confused with mass and weight.

But as per pure science & engineering terminology, weight is the mass time gravitational acceleration or force due to gravity.

That means weight is depend on gravity and here we have mass 78 kg on earth so for weight we have mass 78 kg times gravitational acceleration ( considering costant everywhere on earth) as 9.81 meter per second square.

So, Weight = 78 * 9.81 = 765.18 ~ 765 Newton ( or say kg meter per second square) is answer.