Question 1210373
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x = sum of the three scores after the lowest score was dropped, i.e. we ignore the lowest score
x/3 = 90 = mean of those three scores
x = 3*90 = 270


y = lowest score that was dropped
x+y = sum of four test scores
(x+y)/4 = 70
(270+y)/4 = 70
270+y = 4*70
270+y = 280
y = 280-270
y = 10


Answer: 10
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