For this Q:
mean=31
st.dev.=0.8
x=32
Calculate z-score:
z=(x-m)/s = (32-31)/0.8=1.25
This z-score value corresponding to the probability of 0.8944
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We have that
<span>Bisector theorem--------------- >(LM)/(LN)=(OM)/(ON)
therefore
</span>(18)/(10)=(x)/(4)------------------ > x=7.2
the answer is x=7.2