Let x be Jason's age in 2005
3x be Cora's age in 2005
Four years back,
Cora's age = 3x-4
Jason's age = x-4
Cora was four times as old as Jason four years ago:
3x-4 = 4(x-4)
Solve for x:
3x-4 = 4x-16
16-4 = 4x-3x
12 = x
Jason's age in 2005 is 12. Therefore, Jason was born in 1993.