21.3 is the correct answer.
Firstly, solve 38C15.
Then solve 42C12.
Compare your answers.
The goal here is to see if 38C15 = 42C12.
Here is the formula:
nCr = n!/(r!(n - r)!
Go for it.
6 is the answer
hope this help
First make the denominators of the fractions the same by multiplying.

×

=

Now we just need to add the fractions together

=

9/6 would be the answer, but it can be simplified further, then converted into decimal form.

÷

=
=1.5 yardsYour final answer is 1.5 yards of ribbon are needed.