To evaluate an expression we have to plugg in the value that is given. Think of the first one

Since the value of x is -2, we substitute the value in the expression

So the first expression has a value of 3 when x=-2.
For the second one we have the expression

For x=1, we have

So the second expression has a value of 10 when x=1.
For the last one we have

where m=-2 and n=3. Then

So the last expression has the value of 1 when m=-2 and n=3.