Use Cramer’s rule to solve for the unknown variables in each of the following 3 × 3 systems of simultaneous equations.

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Use Cramer's rule to solve for the equilibrium level of price P and quantity Q, given Supply: 7P 14Q = -42 Demand: 3P+12Q = 90 Converting to matrix format, where A X = B 14 P -42 728-% 3 12 = 90 |A| -7(12) 14(3) = -126 - Solving for P, the first variable, -42 14 |A|= - =-42(12) 14(90) = -1764 90 12 and Solving for Q, the second variable, and Compare with Problem 4.25. |A|| -1764 P = = = 14 |A| -126 -7-42 |A2|= 3 90 Q = =-7(90) (-42)(3) = -504 |A2| |A| -504 = = 4 -126