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2 2 (11*x - 5) - (10*x - 1) - (3*x - 20)*(7*x + 10) = 124
(11*x-5)^2-(10*x-1)^2-(3*x-20)*(7*x+10) = 124
24 - 90*x + 21*x^2 - (3*x - 20)*(7*x + 10) = 124
24 - 90*x + 21*x^2 + 200 - 21*x^2 + 110*x = 124
100 + 20*x = 0
x = -100 / (20)