Question 1012415
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T=number of triangles; P=number of parallelograms
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T+P=42
T=42-P
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3T+4P=150
3(42-P)+4P=150
126-3P+4P=150
126+P=150
P=24
ANSWER 1: There are 24 parallelograms.
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T=42-P=42-24=18 
ANSWER 2: There are 18 triangles.
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CHECK:
3T+4P=150
3(18)+4(24)=150
54+96=150
150=150
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