If 5x-8=7, what is the value of 5x+8 ( EXPLAINING NEEDED)

You're locked out of your house. the only open window is on the second floor, 25 feet above the ground. there are bushes along the edge of the house, so you will need to place the ladder 10 feet from the house. what length ladder do you need to reach the window?

The mean of 10 values is 19. if further 5 values areincluded the mean becomes 20. what is the meanthese five additional values? a) 10b) 15c) 11d) 22

(-y to the power of 2 - 4y- to the power of 2 -6 y +3)