Hi, seems like the answer is f(x) = x - 4
Edit: this was my original answer, but I was apparently completely out of my mind when I wrote it. The correct answer is f(x) = -4x + 50, as I stated below. I'm very sorry for any trouble I caused
Answer:

Step-by-step explanation:
The initial number of mosquitoes is 400000, and they double each day. This represents an exponential growth equation. If t represent days and P represent the population of the mosquitoes, hence this can be represented by the equation:

Also, the predators eat the mosquitoes at a rate of 40,000 mosquitoes/day. This means that each day, the mosquitoes reduce by 40000t, therefore this can be represented by:

We are given with the sequence -20, -16, -12, -8. From this sequence, we can see that the arithmetic difference is +4, from -(-20 + 16). hence following the arithmetic formula of an = a1 + d *(n-1). Substituting, an = -20 + 4 *(n-1) where n is an integer
Answer: 
Step-by-step explanation:
(a) Given
Sam charge $5 for each dog for a thirty minute walk
For an hour which is double the thirty minutes, it must be double of the same charge.

(b)Given
With $20, Christie sells 100 cups of lemonade with a quarter per cup charge
For 100 cup, she generate a revenue of

So, she earns
that is , her profit is 
Answer:
-80
Step-by-step explanation:
→ Complete the multiplication
20 × 8 = 160
→ Complete the take away
3 - 5 = -2
→ Divide the two answers from each other
160 ÷ -2 = -80