Afew questions on mass !

Hey there! I have the answers but no formulas written like a scientics (or engineer's method or something) you know what I mean

1) a box weights 68 newtons, dertermine its mass ! (6974 Kg)

2) what is the weight of a 3miligram dust ? (2.94 * 10^-5)

3) what is the mass of a man of 800 newtons ? (81.6 Kg)
with how much force is he attracted by the Earth ? (800N)
If he jumps of a cliff, what is his acceleration ? (9.8m/s)

Hello,
for all your questions you have to use following formula:
F = m * g
(Force/weight, mass, gravitational acceleration).

1. m = F / g = 68 [N] / 9.8 [m/^2] = 6.94 kg
2. F = m * g = 0.003 [kg] * 9.8 [m/s^2] = 0,0294 N
3. m = F / g = 800 [N] / 9.8 [m/s^2] = 81.6 kg
In this case weight = force;
His accelerations is gravitational acceleration.