Convert 2/5 to a decimal and you get .4, or 40%. 40% of the band members also sing, so yes, the band has the same number of string instrument players and singers.
Bro I’m so tired of those people answering with links
You are right. In circle equation we have =r² so the correct answer will be C od D. But we have to calculate the center of a circle.

Complete the square:

And we have:

So the answer is C (the same left side of equation).