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г) 21a - 30b = -6 23a - 40b = - 28

д) 6u + 5v = 10 5u - 6v = 49

г) { 21a - 30b = -6 | *4                       д) { 6u + 5v = 10 | *6

    {23a - 40b = - 28 | * (-3)                     { 5u - 6v = 49 | *5

    {84a - 120b = -24                                { 36u + 30v = 60

+                                                          +    

    {-69a +120b = 84                                { 25u - 30v = 245      

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    {15a = 60                                             { 61u = 305   

    {21a - 30b = -6                                    { 6u + 5v = 10

    { a = 4                                                   { u = 5      

    { 84 - 30b = -6                                     { 30 + 5v = 10

    { a = 4                                                   { u = 5

    { -30b = -90                                         { 5v = -20

    { a = 4                                                  { u = 5  

    {b = 3                                                   { v = -4