Plz help me

Step-by-step explanation:

For A, 7x=21, it is asking, 7 multiplied by what number is 21? We can try to figure it out. Let's start with 0.

7(0)≠21

Then 1.

7(1)≠21

7(2)≠21

7(3)=21

Therefore, for question a, the answer is 3.

For question b, it's asking 6 minus what is 2.

With this one, we can say it is 4, since 6-4=2.

Now moving on to B.

a) 2x+4=16

We need to isolate x in order to find it's value.

So we can begin with subtracting 4 from both sides, getting us:

2x=12

Then, if we divide both terms by 2, we get x.

x=12/2

x=6.

b)

3 x (z/4)=9

Again, we need to isolate z.

So, we multiply both sides by 4, getting us

3z=36

then we divide by 3

z=36/3

z=12

c) 16-x=2

Here we simply subtract 16 from each side, then flip the signs to get positive x.

So, 16-x=2

-x=-14

x=14

d) 4k=20

This is essentially asking, 4 times what number is 20?

So we can divide both sides by 4 and get

k=20/4

k=5

answer is the third choice:

3x^5+4x^4+x^3+2x^2-10x-7=0

step-by-step explanation: