Calculate net forces. draw an arrow to show its direction

1. 30+70 = 100 N —>
2. 40-30 = 10 N <—
3. 60-60 = 0 N
4. 18+12-30= 0N

if all arrows are pointing the same way, you add them together. If the arrows are pointing towards each other, you minus the smallest number (sn) from the biggest number (bn) (bn-sm). with the fourth one you calculate the total force of the 2 arrows pointing the same way which is 30 and then you minus the arrow pointing left which is also 30. to determine which force goes which way, you look at what arrow on the question has the greater force

The answer is reflection.