Let's call the stamps A, B, and C. They can each be used only once. I assume all 3 must be used in each possible arrangement. 
There are two ways to solve this. We can list each possible arrangement of stamps, or we can plug in the numbers to a formula. 
Let's find all possible arrangements first. We can easily start spouting out possible arrangements of the 3 stamps, but to make sure we find them all, let's go in alphabetical order. First, let's look at the arrangements that start with A:
ABC
ACB
There are no other ways to arrange 3 stamps with the first stamp being A. Let's look at the ways to arrange them starting with B:
BAC
BCA
Try finding the arrangements that start with C:
C_ _
C_ _
Or we can try a little formula; y×(y-1)×(y-2)×(y-3)...until the (y-x) = 1 where y=the number of items. 
In this case there are 3 stamps, so y=3, and the formula looks like this: 3×(3-1)×(3-2).
Confused? Let me explain why it works.
There are 3 possibilities for the first stamp: A, B, or C. 
There are 2 possibilities for the second space: The two stamps that are not in the first space.
There is 1 possibility for the third space: the stamp not used in the first or second space. 
So the number of possibilities, in this case, is 3×2×1.
We can see that the number of ways that 3 stamps can be attached is the same regardless of method used.
        
             
        
        
        
Answer:   w = 7,  x = 6
Step-by-step explanation:  Solve by substitution
W + b = 13 
rewrite as   b = 13 - w  and substitute that value for b in the second equation
6.5w + 2b = 57.5  Then solve for w
6.5w + 2(13-w) = 57.5 . Distribute 
6.5w + 26 - 2w = 57.5 .  Subtract 26 from both sides. Combine like terms and simplify
6.5w - 2w = 57.5 - 26
4.5w = 31.5  Divide both sides by 4.65
w = 7 .  Substitute 7 for w in the first equation and solve for b
7 + b = 13 . Subtract 7 from both sides
b = 6
 
        
             
        
        
        
Answer:
d-"5"_""__"_'uvyctxycuvycycycyv
 
        
             
        
        
        
Answer:
n = 8.15
Step-by-step explanation:
3/8 is 4 & 3/5 % of what number?
Rewrite this as:    3/8 is (4  3/5)% of what number?
Convert 4 3/5% into a decimal:  0.046
Then write out and solve the equation 3/8 = 0.046n, where n is the unknown number.
Dividing both sides by 0.046, we get n = 8.15
 
        
             
        
        
        
I believe the answer is 4.