What is a Solution to an Equation?
Let's start with the basics: An equation is a string of mathematical symbols stating the equality of two expressions.
Sample Problems
1. The equation x = 5 means "x equals 5."
2. "Two times x plus seven equals three times x" can be written in symbols as 2x + 7 = 3x.
3. The equation 
states that the quantities x/2 – 2 and 10 are equal.
An equation is a claim that two quantities are equal. It's like if someone's all, "Hey man, flammable is the same as inflammable," and you're like, "no way, prove it." Think of that equal sign as "is," so when x = y – 5, we're saying that x is y – 5. An equation is true if those two quantities actually are equal, and it's not true ("false") if those two quantities are unequal. In our example of the gentleman who seems to be concerned about a fire hazard, we would write "flammable = inflammable." If these two terms are exactly equal, then the equation is true.
As it turns out, they are the exact same thing. Probably good to know.
Sample Problems
1. The equation 3 + 1 = 2 + 2 is true, since 3 + 1 and 2 + 2 are both equal to 4.
2. The equation 1 = 0 is false because 1 and 0 aren't the same value.
When an equation contains a variable, the equation may be true for some values of that variable and false for others. A solution to an equation is a value that, when substituted for the variable, makes the equation true. We could say "a piece of fruit drawn at random out of this box is a banana." If some fruits in the box are bananas and some are not, then this statement may sometimes be true and sometimes not. Hopefully true in this case, since potassium is an important part of a balanced diet.
Sample Problems
In the equation 2x = x + 4, we can tell that x = 4 is a solution since 2(4) does equal (4) + 4.
On the other hand, x = 3 is not a solution to the equation 2x = x + 4, since 2(3) doesn't equal 3 + 4.