Question 211409
1.,,,   <1 +<2 = 180,,,,,given  supplementary
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2.,,,   <3 +<4 = 180,,,,,given  supplementary
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3.,,,   <2 = 180- <1,,,,,subst  postulate
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4.,,,   <3 = 180- <4,,,,,subst  postulate
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5,,,<2 = <3,,,,,,,,,,,,,,given
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6,,,180-<1 = 180-<4,,,,,,substitution
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7,,,<1 = <4,,,,,,substraction  and  multiplication  postulate
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Note:  There  is  a  Theorem  that  " if  2  angles  are  supplements  of  equal  angles,,,then the  two  angles  are  congruent"
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