Answer:
Step-by-step explanation:
The system of equations can be written ...
 x + y = 36
 x = 2y
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The system can be solve by substituting for x:
 (2y) +y = 36
 y = 12 . . . . . . divide by 3
 x = 2(12) = 24
There are 24 pairs of Nikes and 12 pairs of Adidas.