Question 480835
treat xi like it was a variable.
it's simpler to just call it x.
your problem is solved in the following manner:
original equation is:
9x + 6(200-x) = 1566
simplify by removing parentheses to get:
9x + 1200-6x = 1566
subtract 1200 from both sides of the equation to get:
9x - 6x = 1566 - 1200
combine like terms to get:
3x = 366
divide both sides of the equation by 3 to get:
x = 122
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i suspect xi is really the ith element in the x array.
as such, it would be denoted as x[i] or x<sub>i</sub>
that doesn't really matter.
the algebra is the same whether you are operating on x or xi or x[i] or x<sub>i</sub>