Question 425826
Carrie is two years less than three times her sister Alicia's age. 
If the product of their ages is 40, how old is Carrie and how old is Alicia?
:
Let's do it like this:
:
"Carrie is two years less than three times her sister Alicia's age."
c = 3a - 2
:
"If the product of their ages is 40,"
a*c = 40
c = {{{40/a}}}
:
Replace c in the 1st equation with 40/a
{{{40/a}}} = 3a - 2
multiply both sides by a, results
40 = 3a^2 - 2a
A quadratic equation
3a^2 - 2a - 40 = 0
Factor this to
(3a + 10)(a - 4) = 0
the positive solution is all we want here
a = 4 yrs is Alicia's age
:
Now I know you can find c by yourself. Check your solutions in both original equations