Check the picture below.
since chords NQ and MP cross the center of the circle at R, that means that those two chords are diametrical chords and the angles made by both are vertical angles and thus twin angles, namely both are 18° as you see in the picture, so the angle NMP in magenta is really 162° + 18° + 18° = 198°, and we know the radius NR is 8.
![\textit{arc's length}\\\\ s=\cfrac{r\pi \theta }{180}~~ \begin{cases} r=radius\\ \theta =\stackrel{degrees}{angle}\\[-0.5em] \hrulefill\\ r=8\\ \theta =198 \end{cases}\implies s=\cfrac{(8)\pi (198)}{180}\implies s\approx 27.6](https://tex.z-dn.net/?f=%5Ctextit%7Barc%27s%20length%7D%5C%5C%5C%5C%20s%3D%5Ccfrac%7Br%5Cpi%20%5Ctheta%20%7D%7B180%7D~~%20%5Cbegin%7Bcases%7D%20r%3Dradius%5C%5C%20%5Ctheta%20%3D%5Cstackrel%7Bdegrees%7D%7Bangle%7D%5C%5C%5B-0.5em%5D%20%5Chrulefill%5C%5C%20r%3D8%5C%5C%20%5Ctheta%20%3D198%20%5Cend%7Bcases%7D%5Cimplies%20s%3D%5Ccfrac%7B%288%29%5Cpi%20%28198%29%7D%7B180%7D%5Cimplies%20s%5Capprox%2027.6)
I think this is more of an opinion question. What someone could solve mentally may not be the same as someone else's.If it were my worksheet, I'd circle all of them but it may be different for you.
At your level, I'd probably circle:
54 - 10
93 - 20
and 39 - 2
The answer is simple to work out you do 3/8 + 1/3
but the denominators are different so you find the lowest common multiple in this case 24 .
the frection is now 9/24 + 8/24 this is 17/24
I changed the fraction by doing this 24(common multiple) divided by 8 (denominator) that's how I got it if you don't understand just ask me
