=61*0.36+0.36*10*3.9=61*0.36+0.36*39=0.36*（61+39）=0.36*100=36
61Ⅹ0.36 +3.6X3.9=6.1Ⅹ3.6 +3.6X3.9=(6.1+3.9)x3.6=10x3.6=36
