which expression can be used to substitute for y in the second equation

Question

1st equation- 3x+y=14

2nd equation- x+4y=3

 

Which expression can be used to substitute y in the second equation

 

 A) 3-4y

 B) 3-x

  C) 14-y/3

 D) 14-3x 

Answer 1

The problem gives two equations (numbered).  In order to "substitute for y in the second equation," we find an expression for y using the first equation.

   1st equation- 3x+y=14

                        y = 14-3x                    [subtract 3x from both sides]

 

Next, where you see y in the second equation, you may substitute for y (that is, put in instead of y) the expression, "14-3x."

That allows you to solve for (find the value of) x.  And, once you have solved for x, you may use either equation again to solve for y.

Answer 2

3x + y = 4              subtract 3x from both sides

y = 14 - 3x

 

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