Part 1: The linear equations are
and

Part 2: Solving the equations, we have,
and

Part 3: Jacob is 4 years old and his mother is 40 years old.
Step-by-step explanation:
Part 1: Let j represent Jacob's age, and let m represent his mother's age.
It is given that, "Jacob's mother is three more than nine times as old as Jacob". Writing it as linear equation, we have,
It is also given that, "In eleven years, his mother will be five more than three times his age". Writing it as linear equation, we have,

Simplifying this, we get,

Thus, the linear equation is

The linear equations are
and

Part 2: Solving the linear equation, we get,
Substituting
in


Simplifying, we get,

Hence,

Substituting
in


Solving the equations, we have,
and

Part 3: Since, j represents jacob and m represents the jacob's mother
Thus, Jacob is 4 years old and his mother is 40 years old.