设铅笔X元,圆珠笔(X+2.9)元,钢笔(X+2.9+5)元.
X+(X+2.9)+(X+2.9+5)=5.7×3
X+X+2.9+X+2.9+5=17.1
3X+10.8=17.1
3X=17.1-10.8
3X=6.3
X=2.1
圆珠笔=X+2.9=2.1+2.9=5元
钢笔=X+2.9+5=2.1+2.9+5=10元
答:铅笔2.1元,圆珠笔5元,钢笔10元.
设铅笔X元,圆珠笔(X+2.9)元,钢笔(X+2.9+5)元.
X+(X+2.9)+(X+2.9+5)=5.7×3
X+X+2.9+X+2.9+5=17.1
3X+10.8=17.1
3X=17.1-10.8
3X=6.3
X=2.1
圆珠笔=X+2.9=2.1+2.9=5元
钢笔=X+2.9+5=2.1+2.9+5=10元
答:铅笔2.1元,圆珠笔5元,钢笔10元.