30× 2,9- 2,9 ×28+ 28×2,7 -2,7×26+ 26×2,5-2,5 ×24+24×2,3-2,3×22=

Question

30× 2,9- 2,9 ×28+ 28×2,7 -2,7×26+ 26×2,5-2,5 ×24+24×2,3-2,3×22=

Answer 1

30× 2,9- 2,9 ×28+ 28×2,7 -2,7×26+ 26×2,5-2,5 ×24+24×2,3-2,3×22=2,9(30-28)+ 2,7(28 -26)+ 2,5(26-24)+2,3(24-22)=2,9*2+ 2,7*2+ 2,5*2+2,3*2=2*(2,9*2+ 2,7+ 2,5+2,3)=2*(5+5,4)=2*10,4=20,8