Congrats on your first question!
Answer: x=57
///////////////////////////////////////////////////////////////////////////////////////////////////////
1/3(3x+9)=60
x+3=60
x=57
I believe it's the last one, but it's a matrix not a vector as the question asks
For this you could name any positive number, 0, or -3,-2,-1.
ex.
2,3,-2
The answer is 21 because 21x21x21= 9261
