Răspuns :
(a/9) + a = 90
10a/9 = 90
a = 90 x 9 /10
a= 81
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(81/9) + 81 = 9 + 81 = 90
10a/9 = 90
a = 90 x 9 /10
a= 81
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(81/9) + 81 = 9 + 81 = 90