Select the correct answer from each drop-down menu. A system of equations and its solution are given system A x-y=7 -3x+9y=-39 solution: (4,-3) complete the sentences to explain what steps were followed to obtain the system of equations below. system B x-y=7 6y=-18

Step-by-step explanation:

x-y=7

-3x+9y=-39

Divide the second equation by 3

-x +3y = -13

Add this to the first equation

x-y=7

-x +3y = -13

0x +2y = -6

Divide by 2

2y/2 = -6/2

y = -3

Now find x

x-y = 7

x -(-3) = 7

x+3 = 7

Subtract 3 from each side

x = 4

(4,-3)

Or by substitution

x-y=7  

solve for x

x = 7+y

-3x+9y=-39

Substitute y+7 in for x

-3(7+y) +9y = -39

Distribute

-21 -3y +9y = -39

Combine like terms

-21 +6y = -39

Add 21 to each side

6y = -18

-2

7 - 9 = -2

reversed:

-2 + 9 = 7

fist on the left goes with the third on the right. second on the left goes with the fourth on the right. third on the left goes with the second on the right. the fourth on the left goes with first on the right