42.86% error was in the scientist's estimation.
Step-by-step explanation:
Given data;
Approx amount = 4 ml
Exact amount needed = 7 ml
Percentage error = 

42.86% error was in the scientist's estimation.
Keywords: error, percentage
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3x - 10 = x + 4 <== ur equation
three times a number.....3x...with the x representing the number
ten less....3x - 10
is the same as...means =
that number (x) increased by 4....x + 4
so we have 3x - 10 = x + 4...
3x - 10 = x + 4
3x - x = 4 + 10
2x = 14
x = 14/2
x = 7....and that number is 7