Respuesta :
To solve an equation for a variable, we mean to "isolate" the variable on one side of the equation ( right or left), in order to solve for the variable we add and subtract constant terms, like 7, 8, 10, or any other constant.
In this case, we have the equation -8-2y=10, so the first step to take is to take the -8 "away" and put it to the other side of the equation ( this is the shortest way but you can take the -2y to the other side of the equation first or perform any other operation that you want that does not alter the equation, but the point is to isolate y), to put -8 in the other side of the equation we have to add it to both sides of the equation because -8+8=0:
[tex]\begin{gathered} -8-2y+8=10+8, \\ -2y=18. \end{gathered}[/tex]Now, notice that y still has a constant next to it, but the goal is to leave y alone, so we check what is it that this constant is doing to y, well -2 is multiplying y so in order to take to the other side of the equation we divide all the equation by -2, because -2/-2=1:
[tex]\begin{gathered} \frac{-2y}{-2}=\frac{18}{-2}, \\ y=-9. \end{gathered}[/tex]That is how one solves an equation for a variable.
Alternative solution:
[tex]\begin{gathered} -8-2y=10, \\ -8-2y-10=10-10, \\ -18-2y=0, \\ -18-2y+18=0+18, \\ -2y=18, \\ y=\frac{18}{-2}, \\ y=-9. \end{gathered}[/tex]Solve x+1=3, for x: first I choose on which side of the equation I want x, I want x on the left side ( could be the right side, it is up to you), second, I observe the equation and notice that there is a number being added to x, the constant is +1, to get rid of the constant I must subtract the constant on both sides of the equation:
[tex]x+1-1=3-1.[/tex]The last step is to simplify:
[tex]\begin{gathered} x+(0)=3-1, \\ x=2. \end{gathered}[/tex]