Normally Distributed Data

Given normally distributed data, μ=65, σ=8, how do I find the answer to:
P(70 ≤ x ≤ 80)

P(x1 ≤ x ≤ x2) = 0.2434

P(x ≥ x1) = 0.7157

μ = 65
σ = 8
standardize x to z = (x - μ) / σ
P( 70 < x < 80) = P[( 70 - 65) / 8 < Z < ( 80 - 65) / 8]
P( 0.625 < Z < 1.875) = 0.9699-0.7357 =0.2342
(From Normal probability table)

----------------------------
The middle area is 0.2434
The remaining area is 1-0.2434 =0.7566
Half the remaining area = 0.7566/2 =0.3783

Area below x2 = 0.2434+0.3783 =0.6217
Find z such that P( z < ? ) = 0.6217
z=0.31
That is P( -0.31 < z < 0.31) = 0.2434
z = (x-mean)/sd
0.31 = (x2-65) /8
x2 = 8(0.31)+65 =67.48
-0.31 =(x2-65)/8
x1-65 = (8)(-0.31)
x1= 65+(8)(-0.31) =62.52
x1= 62.52
x2 = 67.48

P( 62.52 < x < 67.48) = 0.2434
--------------------------------------…
P( x < x1) = 1- 0.7157 = 0.2843
From the normal table, locate z such that P( z < ? ) = 0.2843
P( z < -0.57) = 0.2843
-0.57 = (x-65)/8
x1=65-8(0.57)
x1 =60.44
P( x ≥ 60.44) = 0.7157