P = 540, the principal
R = 4.4% = 0.044, the rate, simple interest
A = 991.44, the current value
Let x = years that Sally has held the account
Then
P + PRx = A
or
540 + 540*0.044*x = 991.44
23.76x = 991.44 - 540 = 451.44
x = 451.44/23.76 = 19
Answer:
Sally has held the account for 19 years.