Answer:
Answer for #10:

Answer for #1:

Step-by-step explanation:
In order to solve a simultaneous equation using the substitution method you have to:
Use one of the equation and substitute it into the other equation, in this case equation <em>B</em><em> </em>was substituted into equation <em>A</em><em>.</em>
<em>
</em>
Therefore since x = 1 - y, equation A would be:

Step-by-step explanation:
Answer:
She started with 200 stamps
Step-by-step explanation:
Answer:
The standard deviation of weight for this species of cockroaches is 4.62.
Step-by-step explanation:
Given : A different species of cockroach has weights that are approximately Normally distributed with a mean of 50 grams. After measuring the weights of many of these cockroaches, a lab assistant reports that 14% of the cockroaches weigh more than 55 grams.
To find : What is the approximate standard deviation of weight for this species of cockroaches?
Solution :
We have given,
Mean 
The sample mean x=55
A lab assistant reports that 14% of the cockroaches weigh more than 55 grams.
i.e. P(X>55)=14%=0.14
The total probability needs to sum up to 1,



The z-score value of 0.86 using z-score table is z=1.08.
Applying z-score formula,

Where,
is standard deviation
Substitute the values,





The standard deviation of weight for this species of cockroaches is 4.62.