The answer is 2.84 so the best estimate is 3.00<span />
Division I'm pretty sure Try that
3ab - 3a - 8 + 4ab + 8
7ab -3a
<span><span>The probability of all calculators having no defects is 16.8%. The probability of at least one defect is the complement of that probability.
ie an 83.2% probability of at least one defect.</span><span>
</span></span>
435 being the constant means that is what they started with
Hope this helps :)