Question

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

Answer 1

$^1) ~70 - 70 : a = 60 = \ \textgreater \ 70 : a = 70 - 60 = \ \textgreater \ 70 : a = 10 = \ \textgreater \ a = 70 : 10 = \ \textgreater \ \boxed{a = 7} = \ \textgreater \ \underline{S = 7} ^2) ~ 12 + 9 * a = 21 = \ \textgreater \ 9 * a = 21 - 12 = \ \textgreater \ 9 * a = 9 = \ \textgreater \ a = 9 : 9 = \ \textgreater \ \boxed{a = 1} = \ \textgreater \ \underline { S = 1 }$