李阿姨买了x2.4x-1.5x2.4=3.122.4x-3.6=3.122.4x=3.6+3.122.4x=6.72x=2.8答:买了2.8kg
设李阿姨买了X千克X*2.4=1.5*2.4-3.12
设李阿姨买了X千克, 2.4乘(X-1.5)=3.12