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afla numaul necunoscut; 70-70;a=60 ; 12+9xa=21

Răspuns :

[tex]^1) ~70 - 70 : a = 60 = \ \textgreater \ 70 : a = 70 - 60 = \ \textgreater \ 70 : a = 10 = \ \textgreater \ a = 70 : 10

= \ \textgreater \ \boxed{a = 7} = \ \textgreater \ \underline{S = 7}

^2) ~ 12 + 9 * a = 21 = \ \textgreater \ 9 * a = 21 - 12 = \ \textgreater \ 9 * a = 9 = \ \textgreater \ a = 9 : 9 = \ \textgreater \

\boxed{a = 1} = \ \textgreater \ \underline { S = 1 } [/tex]