150/x-120/(x+10)=2通分150(x+10)/x(x+10)-120x/x(x+10)=2150x+1500-120x=2x(x+10)30x+1500=2x^2+20x2x^2-10x-1500=0x^2-5x-750=0(x-30)(x+25)=0x=30或x=-25(舍弃)所以x=30所以甲有30颗
X=30