6:2:3:4
for every 6 pairs of wedges she owns 2 Stillettos, 3 sneakers and 4 sandals
18/6 =3
3*2 =6 stilettos
3*3 = 9 sneakers
3*4 =12 sandals
18 + 6 + 9 + 12 = 45 pairs of shoes
x*-8 would be -8x
then you would divide -8 by both sides
should get a decimal as your answer I believe