No problem. And your result is correct; you should have done it by hand though in order to learn something. There basically are two approaches (although they do in essence the same thing): 1. Manually, write down the three (or N) equations. Then replace one by a linear combination of (some of) the others in such a way that one variable disappears; if you do that for all but one of the original equations, always getting rid of the same variable, you end up with n-1 equations in n-1 unknown values (and one of the original equations); you solve that in the same way, so iteratively you get at a single equation, a single unknown. 2. Theoretically, and progrsammatically, you would formulate the set of N equations using a N*N matrix (in the example the coefficients would be 1,1,1, 1,2,3, 2,3,5) and a size-N array with the known values. Then solve that with one of the known algorithms, Gauss-Seidel is one way, LU-decomposition another (it basically does what the manual approach does, with the added benefit that the intermediate steps get recorded in the L- and U-triangle you obtain. Using those, you could quickly solve any similar problem having the same matrix coefficients but different known values. :)
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