Ray's solution is incorrect.
Here is the correct solution by Edwin:
We will clear of fractions.
Put parentheses around each term and write the
on the right as so
that every term will be a fraction:
The LCD of all the denominators is
Multiply every term through by
Cancel the 7 into the 28, getting 4
Cancel the 4 into the 28 in the second term, getting 7
Multiply the by the on the right getting
What's left is
The we remove the parentheses by distributing:
The solution set in interval notation is (,)
Edwin