(9x-15)/4=x /*4...... 9x-15=4x........ 5x=15........ x=3
The answer is, 4 + 8 + 12 + 16 ... rule is 4n.
Explanation:
one square has 4 toothpicks, then you added 4 picks (because you started with zero squares).
4 squares have 12 toothpicks, then you added 8 toothpicks to pass from one square to 4 squeres.
If you follow that reasoing you get to realize that the additions are 4, 8, 12, 16.
Answer:
Time taken by the un powered raft to cover this distance is T = 192.12 hr
Step-by-step explanation:
Let speed of boat = u 
Speed of current = v 
Let distance between A & B = 100 km
Time taken in downstream = 32 hours


u + v = 3.125 ------ (1)
Time taken in upstream = 48 hours


u - v = 2.084 ------- (2)
By solving equation (1) & (2)
u = 2.6045 
v = 0.5205 
Now the time taken by the un powered raft to cover this distance

Because un powered raft travel with the speed of the current.

T = 192.12 hr
Therefore the time taken by the un powered raft to cover this distance is
T = 192.12 hr
Cosecθ=sq.rt of 65/8. hope it will help you