Question 98055
The sum of Anne's, Bert's and Chris's age is 60. 
a + b + c = 60
:
Anne is older than Bert by the same number of years that Bert is older than Chris.
a - b = b - c = x
Let x = difference between a & b, and b & c
Then:
b = a-x
c = a-2x

When Bert is as old as Anne is now, Anne will be three times as old as Chris is now.
b + x = a (now)
then find a in terms of x:
(a + x) = 3c
a + x = 3(a-2x); substituted (a-2x) for c
a + x = 3a - 6x
a - 3a = -6x - x
-2a = -7x
2a = 7x
a = 3.5x
:
a + b + c = 60
Substitute for b and c,
a + (a-x) + (a-2x) = 60
3a - 3x = 60
a - x = 20
:
3.5x - x = 20; substituted 3.5x for a, find x
2.5x = 20
x = 20/2.5
x = 8 is the difference
:
a = 3.5x; find a from knowing x
a = 3.5(8)
a = 28 yrs old, then, b = 20 yrs old, and, c = 12 yrs old
:
Check solution from the statement:
"When Bert is as old as Anne is now, Anne will be three times as old as Chris is now.
When B is 28(A's age now), A(28+8) = 3(12(C's age now))
:
Hope this made sense.