It's less confusing if you only think about one of them at a time.
A).
Change the whole thing to all inches.
(Multiply the 8-ft by 12inches/foot.)
Then, when you have it all in one number of inches,
multiply that number of inches by (2.54 centimeters/inch).
B).
1 ounce is the weight of 28.35 grams (on Earth).
Multiply the 300g by (1 ounce / 28.35 g).
C).
Multiply the liters by (0.264 gallon/liter)
Multiply the km by (1 mile / 1.609 km).
Then you'll have a fraction that actually means
(a number of gallons) divided by (a number of miles).
Do the division, and you'll have the gallons per mile.
D).
The area of any rectangle is (length) times (width).
The area of this living room is (13-ft times 14-ft), and that's in square feet.
You know how much 1 square foot of carpet costs.
Just multiply that price by the number of square feet that you need.
A rational number is a number that can be expressed as the relationship between two integers. Fractions and decimals will either repeat or end. An example is 5. Maybe 7. 53573 is an example as well. So is 5/1, because 5 and 1 are both integers. so is 7.5, because 7 and 5 are both integers, and it ends (the numbers after the decimal doesn't keep going). Your answer is 7.8, because it ends.
19/20 in simplest form is 0.95
9/16 in simplest form is 0.5625