x/3+y/5+(3.3-x-y)/5=51/60y/3+x/5+(3.3-x-y)/5=53.4/60

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x/3+y/5+(3.3-x-y)/5=51/60y/3+x/5+(3.3-x-y)/5=53.4/60
x/3+y/5+(3.3-x-y)/5=51/60
y/3+x/5+(3.3-x-y)/5=53.4/60

x/3+y/5+(3.3-x-y)/5=51/60y/3+x/5+(3.3-x-y)/5=53.4/60
由①得:20X+12Y+39.6-12X-12Y=51
由②得:20Y+12X+39.6-12X-12Y=53.4
由①式整理得:20X-12X+12Y-12Y=51-39.6
8X=11.4
X=1.425
由②式整理得:20Y-12Y+12X-12Y=53.4-39.6
8Y=13.8
Y=1.725
∴X=1.425,Y=1.725

方程1减去方程2,消掉公共项(3.3-x-y)/5,而且,x,y的系数一样了,可以求出x,y的关系,再代入方程,就可以最后求出来了

吓唬人方程组,解见图

两边同时乘以60得到20x+12y+39.6-12x-12y=51
8x+39.6=51 8x=11.4 x=1.425
20y+12x+39.6-12x-12y=53.4 8y+39.6=53.4
8y=13.8 y=1.72