Vtyjkyuk

MAIN QUESTION! This is my first question on here so bear with me. I would like to underline my last line of code where it says underline. I have tried to do so as you can see below, but I keep getting an error. I have looked at other posts, but they do not work for my situation as the users are not inside of enumerate or aligned.

For a bonus, I would also like to do the following

1 Align all numbers, operators, variables, andd insert blank spaces for variables not displayed. As shown in the second image below.

2 I would like to have the word solution and the following equations closer to the left because they appear too far to the right.

3 I would like to have a column for each question and/or answer similar to the format shown in the second image below.

4 I would also like to know how I can bring the word solution down without needing to put so many backslashes as shown below.

5 I cannot get the hyphen to appear where it shows exercises 1-4 when I compile my code.

Please note that I am a code minimalist as you can see, aha! So, if it is possible to code in the desired format using a small amount of code that would be much appreciated.

CODE FOR MAIN QUESTION

 begindocument
 beginenumerate
 item
 $
 beginaligned[t]
 x_1+5x_2&= 7 \ 
 -2x_1-7x_2&=-5 \
 endaligned \\\
 textbfSolution: \\
 beginaligned[t]
 x_1+5x_2&=7 \
 -2x_1-7x_2&=-5 \\
 2(x_1 +5x_2&=7) & textReplacement Eq. 2\
 underline+-2x_1-7x_2&=-5
 endaligned
 $
 endenumerate
 enddocument

• please one problem per question ...


• your mwe is not complete and it produce different result from your illustration of problem


• main problem can be solved by use of array instead of the aligned math environment

documentclassarticle
usepackageamsmath
setlengtharraycolsep1pt

begindocument
beginenumerate
item
$
beginarray[t]rl
 x_1+5x_2&= 7 \ hline
-2x_1-7x_2&=-5 \ hline
endarray
$

bigskip
textbfSolution:
$
beginarray[t]rll
 x_1+5x_2 &=7 & \
-2x_1-7x_2 &=-5 & \
2(x_1 +5x_2 &=7) & qquadtextReplacement Eq. 2\
pm 2x_1-7x_2&=-5 & \ cline1-2
endarray
$
endenumerate
enddocument

edit:

• array option [t] align array first row with text row where array is placed(without option the vertical center of array is aligned and with option [b] is aligne bottom array row


• `cline1-2˛draw line from start of first column to end of the second column


• command pm (plus minus) write symbol + over -
  


• i suggest you to read some introductory texts about latex, for example The Not so short Introduction to LaTeX2e or for tables in math as are LaTeX/Tables and LaTeX/Mathematics