1. Nine years ago,the sum of Carlo's age and Ronald's is greater than 28.
Carlo is 6 years older than Ronald. How old is Ronald now?
R = Ronald's age now.
C = Carlo's age now.
R-9 = Ronald's age 9 years ago
C-9 = Carlo's age 9 years ago.
>>...nine years ago,the sum of Carlo's age, C-9, and Ronald's, R-9, is greater than 28...<<
that simplifies to:
>>...Carlo is 6 years older than Ronald...<<
C = R + 6
Substitute R + 6 for C in:
C > 46
R + 6 > 46
R > 40
So thare are many possibilities:
Ronald is 41 and Carlos is 47
Ronald is 42 and Carlos is 48
Ronald is 43 and Carlos is 49
Ronald is 44 and Carlos is 50
Ronald is 45 and Carlos is 51
until the ages get so large that
nobody lives to be that old.
So there is not just one answer. Did you leave
something out?
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2. Group the pairs of terms having a common monomial factor.
The first two terms have a common monomial factor of 3. Since both those terms
are positive, we just group them with a set of parentheses:
The next two terms have a common monomial factor of 4x. Since both those terms
are positive, we just group them with a set of parentheses as before:
The next two terms have a common monomial factor of 5c. Since both those terms
are positive, we just group them with a set of parentheses as before:
The next two terms have a common monomial factor of 5r. Since both those terms
are positive, we just group them with a set of parentheses as before:
Now we have to watch it because the first of the last two terms is a
negative. In that case we insert not just a parentheses but also a
plus sign + and a parentheses before the negative term.
That last pair of factors has common monomial factor 
. If
the first term is negative we always take out a negative.
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Determine the common monomial factor?
We determined them above when we did the grouping. Now we'll factor them
all out, so we have:
Notice that when you factor out a negative as in the last
parentheses, you change both sign inside the parentheses.
Edwin
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