The equation that can be used to determine the number of shirts she bought is
6.85x + 4.50y = 88.65
6.85x + 4.50y = 88.65x + y = z
The total number of hats and shirts isn't given:
let
This can be solved using simultaneous equation
6.85x + 4.50y = 88.65
x + y = z
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