设总共有x支铅笔,则甲1/7x支,乙1/4x支,丙2*(1/4x-1/7x)支
x-1/7x-1/4x-2*(1/4x-1/7x)=11 ( 用总量分别减去甲乙丙的等于剩下的)
x=28
甲:1/7x=4,乙:1/4x=7,丙:2*(1/4x-1/7x)=17
答:甲4支,乙7支,丙17支.
设总共有x支铅笔,则甲1/7x支,乙1/4x支,丙2*(1/4x-1/7x)支
x-1/7x-1/4x-2*(1/4x-1/7x)=11 ( 用总量分别减去甲乙丙的等于剩下的)
x=28
甲:1/7x=4,乙:1/4x=7,丙:2*(1/4x-1/7x)=17
答:甲4支,乙7支,丙17支.