Hello, Alberta!

For years, I used a chart to organize the information.

I'll do the first one . . .

4. Mr. Benny is now 3 times as old as his son.

In 13 years time, he will be twice as old as his son.

Find Mr. Benny's present age.

In the chart, make a row for each person. Code:

- - - - - + - - - - - - - -
Mr. Benny |
- - - - - + - - - - - - - -
son |
- - - - - + - - - - - - - -

Make a column for each time period: "Now" and some other time. Code:

| Now | +13 yrs |
- - - - - + - - + - - - - +
Mr. Benny | | |
- - - - - + - - + - - - - +
son | | |
- - - - - + - - + - - - - +

Mr. Benny is 3 times his son's age.

. . Let $\displaystyle x$ = son's age (now).

. . Let $\displaystyle 3x$ = Mr. Benny's age (now)

Write those in the "Now" column. Code:

| Now | +13 yrs |
- - - - - + - - + - - - - +
Mr. Benny | 3x | |
- - - - - + - - + - - - - +
son | x | |
- - - - - + - - + - - - - +

13 years in the future, both will be 13 years older.

. . Mr. Benny will be $\displaystyle 3x + 13$ years old.

. . His son will be $\displaystyle x + 13$ years old.

Write those in the "+13 years" column. Code:

| Now | +13 yrs |
- - - - - + - - + - - - - +
Mr. Benny | 3x | 3x + 13 |
- - - - - + - - + - - - - +
son | x | x + 13 |
- - - - - + - - + - - - - +

Our equation come from the second column.

In 13 years: .$\displaystyle \underbrace{\text{Mr. Benny}}_\downarrow \:\underbrace{\text{will be}}_\downarrow\: \underbrace{\text{twice}}_\downarrow\:\underbrace{ \text{son's age}}_\downarrow$

. . . . . . . . . . . $\displaystyle 3x + 13\quad\;\; = \quad\;\;\: 2 \:\times \;(x + 13)$

And *there* is our equation!

Solve for $\displaystyle x$, but don't forget:

. . they asked for Mr. Benny's age $\displaystyle (3x)$.