To solve for C, you have to get both of the numbers with a C on the same side. So, subtract the 5c from the right side onto the left side.

Then, divide by 3 on each side.

So, c = 7.
She can cut up the 18 yards into 162 Pisces of 4 inches each. From those, if she works carefully, she can make 81 pairs of little Bootes.
Do a proportion
65/100= x/80
Cross multiply and divide
80 x 65= 5, 200
5, 200 divided by 100 is 52
52 members left
80-52= 28
Answer is 28 members