Question

Chalk contains 3 percent carbon 10 percent calcium and oxygen find the amount in grams of each of these substances in 1 kg

Answer 1

3 % C
10 % Ca
87 % O

Like no way
CaCO3
40 + 12 + 48 = 100 molar mass
40% Ca, 12% C , 48% O
so the real answer is
400 g , 120 g 480 g

BUT using your strange numbers:

in 100 grams:
.03 * 100 = 3 g
.1 * 100 = 10 g
.87 * 100 = 87 g

Answer 2

ans is 120 grams carbon,400 grams calcium and 480 grams oxyzen