Question 931492
Let x = The number

A number squared is equal to 110 less than 21 times the number.
x^2=21x-110
x^2-21x+110=0
(x-11)(x-10)=0
x=11
or
x=10

Substitute x for 11
11^2=21(11)-110
121 =231-110
121 =121

Substitute x for 10
10^2=21(10)-110
100 =210-110
100 =100

The width can either be 11 or 10.