Answer :
Given:
Ricardo is 4 years less than twice as old as his sister.
The sum of their ages is 20.
To find:
Ricardo's age.
Explanation:
Let R be Ricardo's age.
Let S be his sister's age.
According to the question,
[tex]\begin{gathered} R=2S-4............(1) \\ R+S=20...........(2) \end{gathered}[/tex]Substituting equation (1) in (2) we get,
[tex]\begin{gathered} 2S-4+S=20 \\ 3S-4=20 \\ 3S=24 \\ S=8 \end{gathered}[/tex]Substituting S = 8 in equation (2) we get,
[tex]\begin{gathered} R+8=20 \\ R=12 \end{gathered}[/tex]Therefore, Ricardo's age is 12.
Final answer:
Ricardo's age is 12.