Please answer correctly and write explanation

the 3rd choice,   10x + 5, looks good

Step-by-step explanation:

a coefficient is the number in front of a variable , so that's 10

a constant is a number w/o a variable ...  so that's 5

I believe that the answer is 10x + 5.

Coefficents are also know as "multipliers". They pair with variables (in this case, that is x). Constants are simply numbers on their own.

Hope that makes sense.

y is directly proportional to x

Step-by-step explanation:

if y is directly proportional to x it has to have a constant which is k