Do you know what the dashes and the wedges indicate? The dashes indicate that something, in this case a methyl group, is going into the plane. A wedge indicates that something is coming out of the plane. If you have a model set I suggest you make a model- it will become immediately clear which ones are trans
and which ones are cis
because in cis
all the methyl groups will be on one side (the drawing will either have all dashes or all wedges) and in trans
at least one of them will be on the other side (so you will have wedges mixed with dashes).
But yeah- if you don't have a model set get one! A model set makes problems like this easy