Answer:
Step-by-step explanation:
You would never buy a 10-pack, because two 5-packs cost less. 
To buy 3 bars you need a single bar and a pair of single bars for £0.82 + £0.82+ £0.41 = £2.05
To buy 30 bars you need 3 pairs of 5-bar packs = 3×£5.75 =  £17.25
To buy the remaining 5 bars you need one 5-bar pack = £3
cost = £2.05 + £17.25 + £3 = £22.30
 
        
             
        
        
        
First you have to write the equation. in the scenario, use standard form. 
Ax+By=C
plug the numbers in. A=2.50, B=1.25, and C is the total, 356.25. the 180 doesn't come in quite yet.
your equation is 2.50x+1.25y=356.25. now, since they only bought 180 items, you can't go past that.
I am sorry, but I am about to leave for school, and therefore do not have enough time to answer the last of your question. I hope the part I could answer has helped you.
        
             
        
        
        
The x- intercept is where y = 0 on the graph and the y- intercept is where x= 0 on the graph. When X=0, all the terms, except for the constant are equal to zero, thus the y- intercept is the constant. y=10 when x=0. Use the quadratic formula to find the x value where y=0. 
x= (-b +or- sqrt(b^2 -4ac))/2a
y=ax^2 +bx +c
The answer for the x- int is imaginary. This happens because 10 is the parabola's minimum value and it never touches the x- axis. y-int is 10
        
             
        
        
        
Answer:
1. b ∈ B 2. ∀ a ∈ N; 2a ∈ Z 3. N ⊂ Z ⊂ Q ⊂ R 4. J ≤ J⁻¹ : J ∈ Z⁻
Step-by-step explanation:
1. Let b be the number and B be the set, so mathematically, it is written as 
b ∈ B.
2. Let  a be an element of natural number N and 2a be an even number. Since 2a is in the set of integers Z, we write 
∀ a ∈ N; 2a ∈ Z
3. Let N represent the set of natural numbers, Z represent the set of integers, Q represent the set of rational numbers, and R represent the set of rational numbers.
Since each set is a subset of the latter set, we write 
N ⊂ Z ⊂ Q ⊂ R .
4. Let J be the negative integer which is an element if negative integers. Let the set of negative integers be represented by Z⁻. Since J is less than or equal to its inverse, we write 
J ≤ J⁻¹ : J ∈ Z⁻