Answer:
the 2nd is the answer
Step-by-step explanation:
4x + 9 = 2x - 1
4x - 2x = -1 - 9
2x = -10
x = -10/2
x = -5 <===
Answer: 51 notes span 6 octaves.
Step-by-step explanation:
The word "octave" is a Latin word that means "eight".
In an instrument, Each octave is made up of 8 musical notes.
If we have 51 notes , the number of octaves can be made in it = 
![=6.375\approx6\ \ \ \ \ \text{[Rounded to the nearest whole number]}](https://tex.z-dn.net/?f=%3D6.375%5Capprox6%5C%20%5C%20%5C%20%5C%20%5C%20%5Ctext%7B%5BRounded%20to%20the%20nearest%20whole%20number%5D%7D)
Hence, 51 notes span 6 octaves.
These all should be correct
21x(9)=9x21
21y= 9x21
Y=9x21/21
Y=9x1
Y=9