Being X the number of elephant ears Preston ate, X - 2 is the number Vincent ate, thus
X + X - 2 = 8
Joining like terms:
2X - 2 = 8
Adding 2 to each side of the equation
2X - 2 + 2= 8 + 2
Operating
2X = 10
Solving for X
X = 10 / 2 = 5
Thus, Preston ate 5 elephant ears and Vincent ate 5 - 2 = 3 ears