Witch property does 21 times 9 equals 9 times 21

Let w=23 . what is the value of w + 45 ?

Television sizes are based on the length of the diagonal of the television's rectangular screen. so, for example, a 70-inch television is a television having a diagonal screen length of 70 inches. if a 70 inch television's diagonal forms a 29°angle with the base of the screen, what is the vertical height (1) of the screen to the nearest inch? 70 inhin

If you are trying to move an attached term across the equal sign (=), what operation would you use to move it?