Respuesta :
Swap x and y, then solve for y.
x = 3y + 9
x - 9 = 3y . . . . . . subtract 9
(1/3)x - 3 = y . . . divide by 3
This matches the last selection
y = 1/3x - 3
x = 3y + 9
x - 9 = 3y . . . . . . subtract 9
(1/3)x - 3 = y . . . divide by 3
This matches the last selection
y = 1/3x - 3