Răspuns :
( 78×10+a ) : 750 - 318 = 457
780 + a : 750 - 318 = 457
780 + a : 750 = 457 + 318
780 + a : 750 = 775
780 + a = 775 × 750
780 + a = 581.250
a = 581.250 - 780
a = 580.470
( 78×10+a ) : 750 - 318 = 457
780 + a : 750 - 318 = 457
780 + a : 750 = 457 + 318
780 + a : 750 = 775
780 + a = 775 × 750
780 + a = 581.250
a = 581.250 - 780
a = 580.470