<span>The three types of seismic waves produced by an earthquake are primary, secondary, and (D.) surface.</span>
Take east to be the positive direction. Then the resultant force from adding <em>F</em>₁ and <em>F</em>₂ is
<em>F</em>₁ + <em>F</em>₂ = (-45 N) + 63 N = 18 N
which is positive, so it's directed east.
To this we add a third force <em>F</em>₃ such that the resultant is 12 N pointing west, making it negative, so that
18 N + <em>F</em>₃ = -12 N
<em>F</em>₃ = -30 N
So <em>F</em>₃ has a magnitude of 30 N and points west.
<u>Answer:</u> The weight of the object is 29.4 N
<u>Explanation:</u>
To calculate the weight of the object, we use the equation:

where,
m = mass of the object = 3 kg
g = acceleration due to gravity = 
Putting values in above equation, we get:

Hence, the weight of the object is 29.4 N
D. Unbalanced forces are acting on it.
hope this helped