The formula for circumference is

.
To express the circumference exactly, plug the diameter in for

and put the

symbol in front of it. Don't multiply. This expresses the exact circumference.
Say you have the diameter of 17.
You can express the circumference with 17

.
You could convert them into improper fractions first. 7 7/8 should become 63/8 and 3 1/4 should become 13/4. Then, change both fractions so they share a common denominator. I'll use 8.
63/8-26/8 = 37/8, which is then converted into 4 5/8.
Hope that helped you.
Answer:
2x+ 2.1 = 7.5
x=2.7
Step-by-step explanation:
The perimeter of an isosceles triangle with sides x and y is
2x+y = P
I put y as the single side since the question said y is the shortest side. It should say shorter sides if the two sides with the same length are smaller than the third.
We know y =2.1 and P = 7.5
Substituting these values in, we get
2x+ 2.1 = 7.5
Subtract 2.1 from each side
2x+2.1 -2.1 = 7.5 -2.1
2x= 5.4
Divide each side by 2
2x/2 = 5.4/2
x = 2.7 m
That answer is a 1 in 8 chance