Answer:
3 * (x + 7)
Step-by-step explanation:
Mark number as x
Then the sum of a number and seven is x + 7
Three times x + 7 can be written as
3 * (x + 7)
Parentheses mean that we first add x and 7 and then multiply their sum by 3
Alternatively you can write it as 3x + 21, since
3 * (x + 7) = 3 * x + 3 * 7 = 3x + 21
Answer:

Step-by-step explanation:
I am assuming that you are asking what is [x] - 5 if f(86).
When you have this kind of question, what you do is to substitute the variable inside the parenthesis, so like what is says, f(x). If the question replaces the variable x with 86, that means you input the number into the equation.
So [x] - 5, if f(86).
Substitute:
86 - 5

I think it will be 50 so that means is f
We presume you want to add the two vectors.
<5, -2> + <0, 0> = ((5+0), (-2+0)> = <5, -2>