1 Pre college need help

Which problem could be  solved  by evaluating the expression  7×(−3)7×-3?

1. what are the missing reasons in the proof 2. it's in the second picture and 3

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