The percent increase is 75%.
Explanation:
Given,
Initial length of Molly's hair = Old value = 20 inches
Length after three years = New value = 35 inches
Change = New value - Old value
Change = 35 - 20 = +15 inches
The positive sign indicates increase.
Percent increase =
Percent increase =
Percent increase =
Percent increase = 75%
The percent increase is 75%.