What is 921-588? im in fifth grade but its too hard for me

Ihave trouble finding the nth term of a linear sequence

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

Prove that the value of the expression 7^8–7^7+7^6 is divisible by 43.