2x - 3 = sally's berries
x= jim's berries
2x - 3 + x = 21 } equation
3x - 3 = 22 } simplified
+3 +3
3x = 25
---- ----
3 3
x = 8
21 - 8 = 13
sally picked 13 apples
Subtract 16 to get
x^2 -25 = 0
Factor this as
(x -5)(x +5) = 0
The zero product property tells you the product will be zero when one of the factors is zero.
For x-5 = 0
x = 5
For x+5 = 0
x = -5
The appropriate choice is
3) x=-5 or x=5
