Answer:
0N
Explanation:
When you draw a free body diagram, You have a 7N arrow pointing left, and a 3N arrow pointing right. When you subtract the two, you still have a force of 4N on the left. However, seeing as how gravity is in play at a force of 4N, the two forces cancel out and you get 0N.
Answer:

Explanation:
The speed of a wave in a string is given by:

where
T is the tension in the string
m is the mass of the string
L is the length
In this problem, the mass of the string is increased to 2m: m' = 2 m, while the length is not changed, L'=L. If the tension in the string is not changed, then the new speed of the wave in the string will be:

so, the speed of the wave decreases by a factor 
D. 980, this is the best answer because 35 x 7 is 980 :)
1) push down on the end of the lever, and 2) 3/4 of the way from the fulcrum