We know that
1 yard = 3 feet = 36 inches
To solve these types of problems, it's easiest to convert the number into one unit, and then compare.
1) Compare 5 yards to 5 feet
Let's convert to feet.
5 yards * 3 feet per yard = 15 feet
5 feet = 5 feet
Because 15 > 5, we know that 5 yards > 5 feet.
2) Compare 7 inches to 3 feet.
Let's convert to inches.
7 inches = 7 inches
3 feet * 12 inches per foot = 36 inches
Because 36 > 7, we know that 3 feet > 7 inches.
3) Compare 3 feet to 50 inches.
Let's convert to inches.
3 feet = 36 inches (we already did this above)
50 inches = 50 inches
Because 50 > 30, we know that 50 inches > 3 feet.
4) Compare 21 feet to 4 yards.
Let's convert to feet.
21 feet = 21 feet
4 yards * 3 feet per yard = 12 feet
Because 21 > 12, we know that 21 feet > 4 yards.
5) Compare 9 yards to 9 inches.
For this problem, we don't need to do any calculations.
We know that a yard is bigger than an inch, and therefore because there are equal amounts of these units, 9 yards > 9 inches.
6) Compare 36 inches to 3 feet
Let's convert to inches.
36 inches = 36 inches
3 feet * 12 inches per foot = 36 inches
Because 36 = 36, we can conclude that 36 inches = 3 feet.
I hope this helps!