remember that (ab)(cd)=(a)(b)(c)(d)
also remember that 
so






Answer: 25 computers will be selected
Step-by-step explanation:
Where: Z -value at 95% confidence = 1.96; SD = Standard deviation = 10 minutes; N = Sample size; Margin error = 4 minutesSubstituting;4 = 1.96*10/Sqrt (N)Sqrt (N) = (1.96*10)/4 = 4.9N = 4.9^2 = 24.01 ≈ 25
30+x=42 I think because it's has to equal 42 and he already has 30