Answer:
3x+20+(3x-20)=180(linear pair)
or,3x+20+3x-20=180
or6x=180
orx=180÷6
x=30
D=3x+20
=3×30+20
=90+20
=110
A=3x-20
=3×30-20
=90-20
=70
B=x+20
=30+20
=50
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