Let Casey's age be x
Brian's age will be -3 from 2 times x ( Casey's age ) so it will be 2x-3
Adam's age will be Casey's age (x) + 9 which is x+9
NOW the sum of all these ages is 46 so..
Casey's age + Brian's age + Adam's age = 46
x + 2x-3 + x+9 = 46
2x + x + x + 9 -3 = 46
4x + (9 - 3) = 46
4x - 6 = 46
now transfer the numbers on the left one by one to the other side( right )
4x = 46 - 6 ( always remember the sign of the number becomes the opposite when we transfer them to other side)
4x = 40
x = 40 / 4
x = 10
so x = Casey's age = 10
2x - 3 = Brian's age = 2 * 10 - 3
= 20 - 3 = 17
x + 9 = Adam's age = 10 + 9 = 19
