Answer:
Fred is 28, and Natalie is 12.
Explanation:
Let f = Fred's age, and let n = Natalie's age.
f + n = 40
f + 3n = 64
Subtract the first equation from the second equation.
2n = 24
n = 12
f + n = 40
f + 12 = 40
f = 28
Fred is 28, and Natalie is 12.