a)

$\underset{80}{\underbrace{\text{LXXX}}}\underset{5}{\underbrace{\text{V}}}=80+5=85$

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b)

$\underset{60}{\underbrace{\text{LX}}}\underset{8}{\underbrace{\text{VIII}}}=60+8=68$

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c)

$\underset{700}{\underbrace{\text{DCC}}}\underset{20}{\underbrace{\text{XX}}}\underset{4}{\underbrace{\text{IV}}}=700+20+4=724$

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d)

$\underset{900}{\underbrace{\text{CM}}}\underset{40}{\underbrace{\text{XL}}}\underset{6}{\underbrace{\text{VI}}}=900+40+6=946$

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e)

$\underset{600}{\underbrace{\text{DC}}}\underset{80}{\underbrace{\text{LXXX}}}\underset{8}{\underbrace{\text{VIII}}}=60+80+8=688$

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f)

$\underset{500}{\underbrace{\text{D}}}\underset{4}{\underbrace{\text{IV}}}=500+4=504$

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g)

$\underset{1000}{\underbrace{\text{M}}}\underset{500}{\underbrace{\text{D}}}\underset{90}{\underbrace{\text{XC}}}\underset{9}{\underbrace{\text{IX}}}=1000+500+90+9=1599$

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h)

$\underset{2000}{\underbrace{\text{MM}}}\underset{900}{\underbrace{\text{CM}}}\underset{90}{\underbrace{\text{XC}}}\underset{1}{\underbrace{\text{I}}}=2000+900+90+1=2991$