Are all lines of symmetry also diagonals? explain

No, if we think about the lines of symmetry in a square we can see that although all of the diagonals are lines of symmetry there are also two that perpendicularly bisect the edges of the square, these are not diagonals. Also If we consider a rectangle we can see that the diagonals of a rectangle are not lines of symmetry.

1.17+3.99a. you combine the terms with a to create 3.99 and the 1.17 stays because it has no like terms or a variable