Question

Kendra was given this system of equations.

Negative 3 x + 7 y = negative 15. Negative 2 x minus 7 y = 5.

Kendra’s work is shown in the table. Where, if anywhere, did Kendra first make a mistake?

Steps
Kendra’s Work

Step 1

Negative 3 x + 7 y = negative 15. Negative 2 x minus 7 y = 5. Negative 5 x = negative 10.

Step 2

Negative 5 x = negative 10. x = 2.

Step 3

Negative 3 (2) + 7 y = negative 15. Negative 6 + 7 y = negative 15. 7 y = negative 9. y = Negative StartFraction 9 Over 7 EndFraction = negative 1 and StartFraction 2 Over 7 EndFraction

step 1
step 2
step 3
no mistake

Answer 1

GIVEN :

Kendra was given this system of equations.

$-3 x + 7 y = -15$ and  $-2 x -7y = 5$.

TO FIND :

The steps in Kendra’s work where did she make a mistake.

SOLUTION :

Kendra's work :

Step 1 :

Given equations are  

$-3 x + 7 y = -15\hfill (1)$ and

 $-2 x -7y = 5\hfill (2)$.

Step 2  :

Adding the equations (1) and (2) we get

-5 x = -10.

$x=\frac{-10}{-5}$

∴ x = 2.

Step 3  :

Substitute the value of x in the equation (1) we have,

-3(2)+7y=-15

-6+7y=-15

7y=-15+6

7y=-9

$y=-\frac{9}{7}$

∴ $y=-1\frac{2}{7}$

From Kendra's worked steps she make no mistake.

∴ option d) no mistake is correct.