First, establish what you already know to be true:
[tex]P = 3 + R \\ E = 2R \\ R + E = 81[/tex]
You can use these equations to solve each other. Let's take the last one, [tex]R + E = 81[/tex]. Using the additive property of equality, we find that [tex]R = 81 - E[/tex]. We now know that Mr. Richard's age is 81 minus Mr. Edward's age. If we substitute this equation into the second one, we have [tex]E = 2(81 - E)[/tex]. Now use the distributive property to simplify:
[tex]E = 162 - 2E[/tex], and solve for [tex]E[/tex]:
[tex]E = 162 - 2E \\ 3E = 162 \\ E = 54[/tex].
Now we have a definite age. Use this to find the other two ages:
[tex]R + 54 = 81 \\ R = 27[/tex]
and
[tex]27 = 3 + P \\ -P + 27 = 3 \\ -P = -24 \\ P = 24[/tex].
We now know that Ms. Pacheo is 24, Mr. Edwards is 54, and Mr. Richard's is 27! :D