Answer:
1: 19,6 N | 2: 686 N | 3: 705,6 N
Step-by-step explanation:
Just apply the formula:
1: 2 . 9,8 = 19.6 N
2: (60+10) . 9,8 = 686 N
3: [30 + (6 . 7)] . 9,8
[30 + 42] . 9,8
72 . 9,8 = 705.6 N
Just sum all the weights in the system and then multiply by gravity (9,8 in this case)