Simple Pre- Algebra questions!!! Can someone help?

Question

Find x

4x+5=21

8+x=72

81/11=x

7+5-x=21

82/37.5=x

.31/3.12=x

x+y=39

And can you please explain how you did it. Or show work.

Thank you so much! I feel so stupid asking this question!

Answer 1

It might be hard typing it, but I will try.

Question 1

4x+5=21

4x+5=21

    -5  - 5

---------------

4x=      16

-----     -----

4           4

x=      4

Then you check your work

4(4)+5

4x4=16+5=21

8+x=72

  -8  -  8

--------------

x=   64

Check

8+64=72

8(1/11)=x

8x1/11=

(fraction times fraction so you have to make 8 8/1)

8/1x1/11= 8/11

this one is pretty obvious so you don't really have to check

7+5-x=21

12-x=21

+12 +12

----------------

x=     33

check

7+5-33=

12-33=

12+ -33= -21(it doesn't matter that it came out negative)

I am kinda getting tired so I think you can do the rest by yourself.

always do the subtraction/addition/multiplication/divi... on both sides.

And the reason you always end up with x or any other variable on the left side is cuz (I'll use the first one as an example) 4x divided by four. Since you don't know what x is yet, the fours cancel each other out, leaving only x. I hope this helps! And don't feel bad about asking this question, not everyone is good at math

Answer 2

You're not stupid, you're dishonest.

Re-write the equations so x is on the left.

Then add or subtract the same amount from each side to get rid of all extra terms on the left.

Then divide each side by the coefficient of x (if it has one).

5 and 6 are just calculations of what's shown.

The last one is going to have a y in the answer.

Answer 3

1. 4x   +     5    =     21

    4x   = 21 - 5  =  16        Subtract 5 from both sides

   x = 16/ 4                       Divide both sides by 4                  

   x   = 4                       The answer!!!!

When solving equations you do the same thing to both sides at each step.

2.  8 + x = 72

      x  = 72 - 8 = 64

Keep going like this

The last one can't be solved by the way. You would need to know what either x or y was to start with so you could work out what the other one was.