Answer:
Step-by-step explanation:
Let y represent Yolanda's age now, and let d represent their difference in ages. Then Zachary is now y-d years old.
When Yolanda was Zachary's age (now), Zachary was (y-d) -d. Yolanda is now twice that age:
y = 2(y -2d)
4d = y . . . . . . eliminate parentheses, add 4d-y
__
When Zachary is as old as Yolanda is now, Yolanda will be y+d and the sum of their ages will be 63:
y + (y+d) = 63
2y + d = 63
Using the expression for y from above, we get ...
2(4d) +d = 63
d = 7 . . . . . . . . divide by 9
y = 4d = 28 . . . . Yolanda's current age
y-d = 21 . . . . . . . Zachary's current age
