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Is the orthocenter of a triangle on the inside ?

For the rule of 78, for a 12-month period, the last term in the sequence is 12 and the series sums to 78. for an 10 month period, the last term is and the series sum is . for a 15 month period, the last term is and the series sum is . for a 20 month period, the last term is and the series sum is

Determine if the solution set for the system of equations shown is the empty set, contains one point or is infinite. x + y = 5 x + y = 7 {} 1 solution infinite