using f (x)=7x-5 and g (x)= 4x , what is f (2)- g (4)

a)7

b)-7

c)9

d)-9

Do you see that when we change

f(x) = 7x - 5 

to 

f(2) = 7(2) - 5

we are simply saying to substitute in 2 for x? Well that is what we are doing:

f(2) = 7(2) - 5

f(2) = 14 - 5

f(2) = 9 

Now we find g(4) the same way:

g(x) = 4(x)

g(4) = 4(4)

g(4) = 16

Now we find the difference of the two functions:

f(2) - g(4)

9 - 16

-7

So, the answer is B.

F(2)=7(2)-5=14-5=9
g(4)=4(4)=16
f(2)-g(4)=9-16=-7

f(2)-g(4)=-7
B

C. Yes, because the ratios are equivalent between each pair of values

Explanation: 6:3, 14:7, 20:10