Step 1) Subtract color(red)(40y)40y and color(blue)(50)50 from each side of the equation to isolate the yy term while keeping the equation balanced:
-color(red)(40y) + 40y + 40 - color(blue)(50) = -color(red)(40y) + 50y + 50 - color(blue)(50)−40y+40y+40−50=−40y+50y+50−50
0 - 10 = (-color(red)(40) + 50)y + 00−10=(−40+50)y+0
-10 = 10y−10=10y
Now, divide each side of the equation by color(red)(10)10 to solve for yy while keeping the equation balanced:
-10/color(red)(10) = (10y)/color(red)(10)−1010=10y10
-1 = (color(red)(cancel(color(black)(10)))y)/cancel(color(red)(10))
-1 = y
y = -1
