Please help very urgent!!

For the first one:

 𝑓(𝑥) = −5𝑥 − 8

a. (2,-18)

c. (12,-68)

For the second one :

11.5𝑥 − 2.3𝑦 ≤ 20.8 

a. (-10,10)

c. (0,5)

d. (1,0)

For the third one :

𝑓(𝑥) = −2(0.8)^x+1  

b. (-1,-2)

The explicit rule is  for the nth term  is  :     a_n  =  6*(2)^n-1

OK.......here's the first one

f(x)  =  -5x  -  8

a. (2,-18)

b. (10, -42)

c. (12,-68)

d. (4,28)

Putting 2 into the funnction we get   -5(2) - 8  =  -18

Putting 10 into the function we have  -5(10) - 8  =  -58

Putting 12 into the function we have  -5(12) - 8  = -68

Putting 4 into the function we have  -5(4) - 8  = -28

So......a and c are correct

For the second one, we have

11.5x  -  2.3y ≤  20

11.5 (-10)  - 2.3(10) ≤ 20    ⇒ -138  ≤ 20   which is true

11.5 (10)  - 2.3(-10) ≤ 20    ⇒ 138  ≤ 20   which is false

11.5 (0)  - 2.3(5) ≤ 20    ⇒ -11.5  ≤ 20   which is true

11.5 (1)  - 2.3(0) ≤ 20    ⇒ 11.5  ≤ 20   which is true

So....a, c and d are correct

𝑓(𝑥) = −2(0.8)^x+1

-2(0.8)^{0+ 1} =  -1.6       not true

-2(0.8)^{-1+ 1}  =  -2 (0.8)⁰  =  -2(1)  =  -2   true

-2(0.8)=^{-1.6+ 1}  =  -2(0.8)^-.6  = -2.286  not true

-2(0.8)^{2.8 + 1}  =  -2 (0.8)^3.8  = -0.856  not true

So......only b is correct