Let D = David's present age, A = Anna's present age.

Five years ago David's age was D-5, while Anna's age was A-5, 
and the condition says that

D-5 = 4*(A-5).

This is your first equation.

The second is

D + A = 25.

Now express D = 25 - A from the second equation and substitute it into the first. You will get

(25-A) - 5 = 4*(A-5).

Simplify and solve it:

30 - A = 4A - 20,

20 + 20 = 4A + A,

5A = 40,

A =  = 8. 

Thus Anna is 8 years now. 
Hence, David is D = 25 - A = 25 - 8 = 17 years now.

 

RELATED QUESTIONS

3.	The sum of the ages of Daniel and Ann is 25. Five years ago David was four times as... (answered by Fombitz)

The sum of the ages of David and Ann is twenty-five. Five years ago David was four times... (answered by josgarithmetic)

A man is three times as old as his son. Eight years ago the sum of their ages was 36.... (answered by vleith)

Allen is three times as old as Betty, and Luz is five years younger than Allen. Three... (answered by JulietG)

Michelle is twice as old as Anna. If five years ago the sum of their ages was 62, how old  (answered by jim_thompson5910)

ten years from now, Anna will be twice as old as Barbara. Five years ago, Anna was three... (answered by ankor@dixie-net.com)

sonny is twice as old as david. Four years ago, he was four times as old as david. When... (answered by mananth,josmiceli,ikdeep)

Anna is four times as old as Matt, the sum of their ages is 65 years. how old are they  (answered by ikleyn,stanbon)

Vanda’s present age is three times that of his son. Nine years ago he was five times... (answered by MathLover1)