I have been out of math for years and I am stuck on 3-4 problems of my first struggle since returning to school

10x(to the 9th power) = 2x( ) I think it's 5x to the 8th power but am I forgetting some rules or something?

x(to the 2nd power) + 27 + 28 I believe it's prime but I may be wrong. none of the other answers work out for me or is it (x+28)(x-1)

how do I work out something like x(to the 4th power) -1