Hi Normal Distribution: μ = 0 and σ = 1 using a TI or similarly an inexpensive calculator like a Casio fx-115 ES plus: If P(-b > z < b) = 0.12 ⇒ 2P(z ≤ -b)= .12 and P(z ≤ -b) = .06 invNorm(.06) = -1.5548 ⇒ b = 1.5548 Wish You the Best in your Studies.