Question

Anca si Diana au impreuna 90 de lei , Anca si Radu au impreuna 79 de lei , iar Diana si Radu au impreuna 97 lei . Cati lei are fiecare copil ?

Answer 1

A + D = 90
A + R = 79
D + R = 97
2A + 2D + 2R = 266
2 ( A + D + R ) = 266
A + D + R = 266 : 2
A + D + R = 133
A + 97 = 133
A = 133 - 97
A = 36 ( LEI ARE ANCA)
A + R = 79
36 + R = 79
R = 79 - 36
R = 43 ( LEI ARE RADU)
A + D = 90
36 + D = 90
D = 90 - 36
D = 54 ( LEI ARE DIANA)

Answer 2

Fie Anca x Diana y Radu z. atunci x+y=90. y=90-x. y=90-x x+z=79. z=79-x z=79-x y+z=97. 90-x+79-x=97. -x-x=97-90-79 y=90-x. y=90-x. y=90-36 z=79-z. z=89-x. z=79-36 -2x=-72. x=36. x=36 y=54. Din condtiile puse la inceputul z=43. Problemei:Anca are 36lei x=36. Diana are 54 lei Radu are 36lei