Answer:
Mark is 12 years old.
Explanation:
Let's just define some variables:
J = Jason
A = Alex
M = Mark
Next, let's put the information given in the question into equations.
Since Jason is 10 years older than Alex we can represent it like this:
J = A + 10
Since Mark is 11 years younger than Alex we can represent it like this:
M = A - 11
All of their ages add up to 68 so we can represent that like this:
J + A + M = 68
We can now do some substitutions to the J and M in this equation, like this:
(A + 10) + A + (A - 11) = 68
Combine like terms:
3A - 1 = 68
Solve for A
3A = 69
A = 23
Now that we found that Alex is 23 we can plug that back in to the first equations to find their ages:
J = 23 + 10
J = 33
M = 23 - 11
M = 12
Mark is the youngest out of the siblings being 12 years old.
Check:
23 + 33 + 12 = 68
68 = 68 :)
I hope this helps!!
- Kay :)