Can you please help me with A and B

I read:
Farm Maid Yogurt : 6 g of fat in 13 cups
Dairy Delight Yogurt: 5 g of fat in 11 cups.

(This is what I read, which does not represent realistic numbers, likely decimals are missing).

(a) Farm Maid Yogurt
6 g/13 cups = 10 g/x cups
Cross multiply: 6x = 130 => x=130/6=21.67 cups.

(b)
Farm maid : 6 g/13 cups, 6/13 in 13/13 cups => 0.4615 g/cup
Dairy Delight : 5 g / 11 cups, 5/11 in 11/11 cups => 0.4545 g/cup
=> Dairy Delight Yogurt has slightly less fat.

(c) 9 cups of Dairy Delight
5 g / 11 cups = x g / 9 cups
Cross multiply
11x=5*9 g => x=5*9/11 g = 4.09 g

(d) 3 cups of Dairy Delight & 5 cups of Farm Maid.
5 g/ 11 cups = x g / 3 cups
Cross multiply
x=5*3/11 = 1.3636 g

5 cups of Farm Maid
6 g / 13 cups = y g / 5 cups
Cross multiply
y=6*5/13=2.3077 g

Total fat consumed = 1.3636+2.3077 g = 3.6713 = 3.671 g (to the nearest thousandth gram).