How do you start this and find the weight of each shape? i do not remember doing this in class.

Let's say   make the shapes, some variable name

say   

⛁    ⚪     ◽    ▯
a     b      c     d

so.. if take those are the shapes provided

then we can take a look at the first set and we can say that

2a + b + c = 20

a + 4d + b = 19

a + c = 9

3c + d + a = 19 

thus     

and surely you can find the other two

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