You can put this solution on YOUR website! Evaluating an express means doing the math. In the first case you have which means multiply 3 by itself 2 times. So you have the equivalent expression 3 x 3. Can you do this math?
In the second case you have a + 2 where you are using "a" to replace a number. You don't know what the number is, so you use a "name" for it. Then someone tells you that a is really 1 (a=1). So the equivalent expression is
1 + 2. You have replaced the name "a" with the value it represents ("1"). Can you do this math?
Always think of unknowns in algebra as numbers. When you see x + 2 = 7 it means
"Some number, that I'm calling 'x' for now since I don't know what it is, when added to 2 equals 7." Can you guess what number 'x' is?
Well, you don't have to guess. Sometimes it is very hard to guess. There are ways to figure out what 'x' is without having to guess. That's algebra!
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