Answer: 10
<u>Step-by-step explanation:</u>
varies directly means: 
Step 1: solve for k ⇒ 
Step 2: plug in the given value and k to solve for the missing value: 
42(5) = 21(x)

2(5) = x
10 = x
Answer: A. As x → ∞, f(x) → ∞, and as x → –∞, f(x) → ∞.
Step-by-step explanation:

Subtract 5/8 on both sides
To subtract 5/8 we make the denominators same

Addition or Subtraction property of order is used

Subtract 4x on both sides
Addition or Subtraction property of order is used

Now divide both sides by -1
Multiplication or Division property of order is used

Multiplication or Division property of order is used

Hello from MrBillDoesMath!
Answer: infinite solutions
Discussion: I did a double take on this one but the left hand is
a + 3 + 2a = 3a +3
and the right hand side is
-1 + 3a + 4 = 3a + (4-1) = 3a + 3
The left and right sides of the equation are identical for all "a", i.e. for infinitely many "a" values.
Regards, MrB.