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a fost răspuns

mihaela,alexandra si costin au strans o suma de bani.mihaela si alexandra au 324 lei, alexandra si costin au 362 lei , iar mihaela si costin 312 lei. ce suma a pus fiecare?

Răspuns :

M+A+C=?

M+A=324
A+C=362
M+C=312 => adunam cele trei relatii
__________
2M+2A+2C=998 /:2 => dam factor comun pe 2 => M+A+C=499

324+C=499
C=499-324
C=175

362+M=499
M=499-362
M=137

A+312=499
A=499-312
A=187
m+a+c=x ,unde m=Mihaela ,a=Alexandra,c=Costin,x= suma de bani stransa  impreuna
m+a=324
a+c=362
m+c=312
2m+2c+2a=324+362+312
2m+2c+2a=998
impartim totul la 2 si avem:m+c+a=499
deci x=499
324+c=499  c=499-324=175
m+362=499 m=499-362=137
a+312=499 a=499-312=187
Alexandra=187 lei,Mihaela=137 Costin 175 lei