Answer:
A) 100 + 5x = y
10 + 20x = y
Step-by-step explanation:
100 is the amount Andre started with and 5x is the 5 he adds each week
10 is the amount Elena started with and 20x is the 20 she adds we week
Answer:

Second option is correct.
Step-by-step explanation:
We have been given the expression 
We can write the term 64 as 
Thus, we have

Now, use the exponent law 

On simplifying, we get

This expression can be further simplified as

Second option is correct.
Answer:
The value of
is 4.
Step-by-step explanation:
Given:

We have to solve for x.
Solution:

Now by using Multiplication property of equality we will Multiply both by -6 we get;

Now by using Division property of equality we will divide both by 5 we get;

Hence The value of
is 4.
Answer:
525
Step-by-step explanation:
This is a question involving combinatorics
The number of ways of choosing a subset k from a set of n elements is given by
which evaluates to 
n! is the product n × (n-1) × (n-2) x....x 3 x 2 x 1
For example,
4! = 4 x 3 x 2 x 1 = 24
3! = 3 x 2 x 1 = 6
Since we have to choose 4 boys from a class of 6 boys, the total number of ways this can be done is

Note that 6! = 6 x 5 x 4 x 3 x 2 x 1 and 4 x 3 x 2 x 1 is nothing but 4!
So the numerator can be re-written as 6 x 5 x (4!)
We can rewrite the expression 
Cancelling 4! from both numerator and denominator gives us the result
as (6 × 5)/2! = 20/2 = 15 different ways of choosing 4 boys from a class of 6 boys
For the girls, the number of ways of choosing 3 girls from a class of 7 girls is given by

This works out to (7 x 6 x 5 )/(3 x 2 x 1) (using the same logic as for the boys computation)
= 210/6 = 35
So total number of committees of 4 boys and 3 girls that can be formed from a class of 6 boys and 7 girls = 15 x 35 = 525
If the tax rate is 8%, we need to find 108% of the price, or 330 times 1.08, which is $356.4