Solve 3 linear equations in 3 unknowns on a spreadsheet

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The program used is Excel. The steps are:
  1. Enter the matrix of coefficients and the column of constants.
  2. Select a 3-by-3 region to hold the inverse of the coefficient matrix. Enter =MINVERSE(a1:c3) and
  3. press CTRL-SHIFT-ENTER to enter the formula into all cells of the region.
  4. Select a 3-by-1 column to hold the answer, enter =MMULT(a5:c7,e5:e7) and
  5. press CTRL-SHIFT-ENTER to enter the formula into all cells in the column.
  6. If you want the answer in fractional form, you can select the cells where you want fractions, select Format-Cells, and give all the cells the format ????/????.
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