已知(x+1)/2=(y+3)/4=(x+y)/5,得出,(x+1)/2=(y+3)/4 (2x+2)/4=(y+3)/4 则,2x+2=y+3 2x-y=1 .(1) 再将已知条件进行通分,(x+1)/2=(y+3)/4=(x+y)/5 (10x+10)/20=(5y+15)/20=(4x+4y)/20 得出,(10x+10)+(5y+15)=2*(4x+4y)...