Answer :
lets assume the length=y and the width=x
y=x+3
A=xy
A=x(x+3)
A=x^2+3x
154=x^2+3x
0=x^2+3x-154
use the quadratic formula
x=11
x=-14 DNE
therefore the width is 11
y=x+3
A=xy
A=x(x+3)
A=x^2+3x
154=x^2+3x
0=x^2+3x-154
use the quadratic formula
x=11
x=-14 DNE
therefore the width is 11