The biggest number will be positive because positive numbers are greater than negative numbers.
3.5 is bigger than 3.3 so the first two numbers are 3.5, 3.3.
Now we have two negative numbers. -3¾ is more negative than -3⅓ so it’s smaller, because -¾ is smaller than -⅓. (Remember that -3⅓ is the same as -3-⅓ and -3¾ is the same as -3-¾, the fractions and the whole numbers are all negative.)
The final order is 3.5, 3.3, -3⅓, -3¾.