2.4(a - 0,2b + 3,5c)
Make these decimals fractions:
2,4 = 24/10
0,2 = 2/10
3,5 = 35/10
Simplify
24/10 = 12/5
2/10 = 1/5
35/10 = 7/2
Now,
12/5 . (a - b/5 + 7c/2)
Now multiply everything
12/5 . a - 12/5 . b/5 + 12/5 . 7c/2
12a/5 - 12b/25 + 84c/10
Now make the divisions
12/5 = 2,4
12/25 = 4,8
84/10 = 8,4
2,4a - 4,8b + 8,4c
Alternative D.