Mr. jacobs 55 years old and tony is 7 years olds , in how many years will mr. jacobs 4 times as old as tony ?

Call the mystery number of years ' Y ' .

In 'y' years, Mr. Jacobs will be (55+y), and tony will be (7+y).

You said that Mr. Jacobs will then be 4 times as old as tony, so . . .

                                                55 + y = 4 (7 + y)

Eliminate the parentheses:     55 + y = 28 + 4y

Subtract 28 from each side:   27 + y =         4y

Subtract 'y' from each side:    27       =         3y

Divide each side by  3 :           9       =           y

In 9 years, Mr Jacobs will be (55 + 9) = 64.
In 9 years, tony will be (7 + 9) = 16.

64 is 4 times 16, and now that tony has turned 16,
he can start spelling his name with a capital ' T ',
like a regular grown-up.