630-(630-580)x3=630-50x3=630-150=480(元)答：购甲乙丙各一件,共需480元.购甲3件,乙 7件,丙1件,共需580元购甲4件,乙10件,丙1件,共需630元则购甲4-3=1件,乙10-7=3件,丙1-1=0件,共需630-580=50元购甲1x3=3件,乙3x3=9...