Answer:
The least number of stamps required is 
Step-by-step explanation:
Let the number of
cent stamps be
and
cent stamps be 
We have

The minimum number is obtained when more
cent stamps are used
Here
cannot be greater than
since 
Substitute 

Not possible since
is not a fraction
Substitute 

Not possible since
is not a fraction
Substitute 

Possible
Hence minimum number of stamps is

Answer: Sara multiplied by 3 when she should have multiplied by 8.
Step-by-step explanation:
21 : 7*8
7*8 = 56
21 : 56
The simplest form of this ratio is 3 : 8
So, since 100% = 128, x should equal 96, and we are trying to find x.
Multiply both sides of the equation by x.
(100/x) * x = (128/96) * x
Cancel out the x's on the left side so
100 = 1.333(x)
75 = x
96 is 75% of 128
Answer: 9 (with a margin of: 0)
Step-by-step explanation:
Times everything by 5
That gives you 15 + 10w = 105.
Subtract 15 from both sides
Divide by 10 to get w by itself
Then you solve