Question

Help !! What’s the answer ??

Answer 1

A number is n.
The square of a number is n ².
10 times of the square of a number is 10n².

90 times the number is 90n.

10n²=90n
n²=9n
n²-9n=0
n(n-9)=0
n=0,
n-9=0, 
n=9
Non-zero number is 9.

Answer 2

10(x^2) = 90x where x > 0 or x < 0

Factor by 10x on each sides

10x(x) = 10x(9)

x = 9