# find and solve the equation- algebra

• Oct 20th 2012, 07:00 PM
Splits
find and solve the equation- algebra
The sum of Kris and Victor's ages is 27 years. In three years, Victor will be three times as old as Kris. What are their present ages?

Find the solution using only one variable.
• Oct 20th 2012, 07:10 PM
MarkFL
Re: find and solve the equation- algebra
Let \$\displaystyle K\$ be Kris' age and \$\displaystyle V\$ be Victor's age.

The statement "The sum of Kris and Victor's ages is 27 years" becomes what equation?

The statement "In three years, Victor will be three times as old as Kris" becomes what equation?

Post what you think, and we will guide you from there,
• Oct 20th 2012, 07:12 PM
Splits
Re: find and solve the equation- algebra
Thank you very much but I am not allowed to use two different variables. Do you know how i can do it with one variable?
• Oct 20th 2012, 07:20 PM
Splits
Re: find and solve the equation- algebra
I'll try it your way though.
• Oct 20th 2012, 07:22 PM
MarkFL
Re: find and solve the equation- algebra
Well, you are given two unknowns and two statements which are essentially equations, so the easiest way is to use two variables, and the two statements to get a 2X2 linear system.

Are you not studying systems of equations?
• Oct 20th 2012, 07:25 PM
Splits
Re: find and solve the equation- algebra
"The sum of Kris and Victor's ages is 27 years"
y+(27-y)=27
"In three years, Victor will be three times as old as Kris" I got the 1st part i think, but i don't know what goes on the right side of the equation.
27-y+3 (would be victor's age in three years) and y+3 (would be kris's age) but i don't know how to put them together.
• Oct 20th 2012, 07:39 PM
Splits
Re: find and solve the equation- algebra
we are learning how to solve equations with one variable. So 27-y would be the second variable. We have not been using two variables in class, so I don't know if my teacher would be ok with me using more than one.
• Oct 20th 2012, 07:57 PM
MarkFL
Re: find and solve the equation- algebra
Okay, this seems an odd way to go about it, since if we write:

\$\displaystyle K+V=27\$

We find:

\$\displaystyle K=27-V\$

Now, for the second statement, I would write:

\$\displaystyle V+3=3(K+3)\$

Which gives us:

\$\displaystyle V+3=3(27-V+3)=3(30-V)\$

And now I would solve for \$\displaystyle V\$.
• Oct 23rd 2012, 05:32 PM
Splits
Re: find and solve the equation- algebra
Thank you very much for your help! I asked 5 other people and they couldn't do it.