y = -2x - 4
--> Swap sides so that all variable terms are on the left hand side
-2x - 4 = y
--> Add 4 to both sides
-2x = y + 4
--> Divide both sides by -2
-2x/-2 = y+4/-2
--> Dividing by -2 undoes the multiplication by -2.
x = y+4/-2
--> Divide y+4 by -2
x = -y /2 -2
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y = 1/4x + 5
--> Swap sides so that all variable terms are on the left hand side.
1/4x + 5 = y
--> Subtract 5 from both sides.
1/4x = y - 5
--> Multiply both sides by 4.
1/4x 1/4 = y - 5/ 1/4
--> Dividing by 1/4 undoes the multiplication by 1/4.
x = y - 5/ 1/4
--> Divide y - 5 by 1/4 by multiplying y - 5 by the reciprocal of 1/4.
x = 4y - 20
Hope this helps you!