4,2×7,3-4,2×2,7=? 2,1×6,4-2,1×3,6=?

4,2*6,4-2,1*3,6 = 19,32
1) 4,2*6,4 = 26,88
2) 2,1*3,6 = 7,56
3) 26,88-7,56 = 19,32

2,1*6,4-2,1*3,6 = 
1) 2,1*6,4 = 13,44
2) 2,1*3,6 = 7,56
3) 13,44-7,56 = 5,88