The weight of an object is the product of its mass, m, and the acceleration of gravity, g (where g=9.8 m/s2). If an object’s mass is m=10. kg, what is its weight?

You just told us that  Weight = (mass) x (gravity), and that mass=10kg and  gravity = 9.8 m/s². All we need to do is write those numbers in place of the letters.                      Weight = (10 kg) x (9.8 m/s²)  =  98 newtons.