1) get a picture of a baby mobile
2) select a weight for the highest item (label the weight x)( in this example, the giraffe would be x)
3) use other expressions to represent the weight of heavier items (for example) the second item is (x + 3).... weight can be in ounces
4) the lowest item can be 3x - 4 (for example)
5) Then choose sides (all the items on the left side must equal the items on the right side)[the lion +hippo = zebra + elephant]
6) Solve for x
this pic is clear