In 10 years . A will be twice as old as B was 10 years ago. If A is now 9 years older than B, the presents age of B is:

Let's denote the present age of A as "A" and the present age of B as "B."

According to the information provided:

1. In 10 years, A will be twice as old as B was 10 years ago. This can be represented as:

A + 10 = 2(B - 10)

1. A is now 9 years older than B. This can be represented as:

A = B + 9

Now, we can solve this system of linear equations to find the values of A and B.

First, let's rewrite the second equation in terms of A:

A - B = 9

Now, we have the following two equations:

A + 10 = 2(B - 10) A - B = 9

We can solve this system of equations simultaneously. Let's start by solving the second equation for A:

A = B + 9

Now, substitute this expression for A into the first equation:

(B + 9) + 10 = 2(B - 10)

Now, simplify and solve for B:

B + 19 = 2B - 20

19 = B - 20

B = 19 + 20 B = 39

So, the present age of B is 39 years.