Hi Recommend the use of a calculator and understanding of the standard normal curve Normal Distribution: µ = 0 and σ = 1 z score represents the area under the curve to the LEFT of its valueUsing TI or similarly an inexpensive calculator like an Casio fx-115 ES plus Calculator function Invnorm(X) gives value to the LEFT of z Middle 60% |z= Invnorm(20%) = -.84 (to 2 decimal places) Middle 60%: -.84 to .84 | | weight from: 314.46 to 328.44 Highest 80 percent: weight > 314.46 Lowest 15 percent: |z= Invnorm(15%) = -1.04 | weight ≤ 298.36 Wish You the Best in your Studies.