Respuesta :

1.
xy=-45 (divide both sides by x)
xy÷x = 45÷x
y= 45÷x
y= 45/x

2.
x=15/y ( cross multiply)
xy= 15 ( divide both sides by x)
y= 15/x

3.
2xy= 9 (divide both sides by 2x)
y= 9/2x
y= 4.5/x