Answer: Fraction of twins =
Fractions of triplets =
Fractions of quadruplets = 
Step-by-step explanation:
Since we have given that
Number of set of twins = 5
Number of sets of triplets = 2
Number of sets of quadruplets = 1
Total number of sets is given by

Now, we need to find the fraction of those students.
So, Fraction of twins is given by

Fractions of triplets is given by

Fractions of quadruplets is given by

Answer:
Catron's error is
"She did not follow order of operations"
Step-by-step explanation:
Catron evaluates the expression (negative 9) (2 and two-fifths)
That expression can be written as below

Catron's error is
"She did not follow order of operations"
The corrected steps are
Step1: Given expression is 
Step2: Convert mixed fraction into improper fraction
Step3: Multiplying the terms

Therefore solution 
Answer:
Jessica wants 180 plants in her garden.
Step-by-step explanation:
The formula for the area of the triangle is (1/2)*base*height.
So here, Let’s say 8 feet is the base and 15 feet is the height.
the area of the triangle would be (1/2)*8*15. That equals 60 square feet.
If Jessica wants 3 plants each square foot, then 60*3, which is 180 plants.
Note: * means the multiplication sign.