See the attached picture:

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Step 1 -

[ distributive property ]
Step 2 -


Answered by : ❝ AǫᴜᴀWɪᴢ ❞
Answer:

Step-by-step explanation:
We have the equation 
In order to solve for x, we need to get all of the x's to one side and everything else to the opposite side

First, we can add 1 to each side

Now, we can add x to each side

Next, we can divide each side by 2

And here is our answer.
Joanna bought 7 notebooks and 14 pencils
Step-by-step explanation:
Step 1 :
Let x denote the number of notebooks and y denote the number of pencils Joanna bought.
Cost of one notebook = $ 2.30
Cost of one pencil = $1.42
Step 2 :
Total of notebooks and pencils bought = 21
=> x + y = 21 => y = 21-x
Total cost of notebooks and pencils = $35.98
=> 2.3x + 1.42y = 35.98
Substituting y = 21- x here , we have,
2.3x + 1.42 ( 21-x) = 35.98
2.3x + 29.82 - 1.42x = 35.98
0.88 x = 6.16
=> x = 7
y = 21-x = 21-7 = 14
Step 3 :
Answer :
Joanna bought 7 notebooks and 14 pencils