Как вычислить значение дроби 5 а+3 b / 4 a +5 b, если 6a+7b =0"

( 5A + 3B) /( 4A + 5B ) = ? --------------------------- 6A + 7B = 0  6A = - 7B  A = ( - 7/6B )  -------------------------- ( 5 * ( - 7/6B ) + 3B ) / ( 4 * ( - 7/6B ) + 5B ) = ( - 35/6B + 3B ) / ( - 28/6B + 5B ) = = ( - 35/6B + 18/6B ) / ( - 28/6B + 30/6B ) = ( - 17/6B ) / ( 2/6B ) = ( - 17/2 ) = = ( - 8,5 )  Ответ ( - 8,5 )