2x-19=7x+31 20-2t=t-1 19-y=100-10y 1/2x+5=2/3x-6 1/2x-0.2x=1/4x+4 -3x-5/2=3/2x-1 求过程

X=-10 ,2x-7x=31+19 得 -5x=50
t=7,20+1=t+2t 得21=3t
y=9 ,100-19=-y+10y得81=9y
x=66 ,都乘于6得3x+30=4x-36得x=66
x=5/6 都乘于20得10x-4x=5x-90-60x-50=30x-20得x=5/6