book Maths Puzzle Numerical Ability

No matter how I try, I am not understanding this type of problem....
3x -2y + 5z
____
2y -3x -5z

This is how I try....
3x (3x-2y + 5z) -(2y + 5z)
_

Read Solution (Total 0)

book Other Question

the square of a number decreased by the square of one half the number is 108. find the number. A flag pole 20 feet high casts a shadow of 5 feet. At the same time, a nearby building casts a 20-foot shadow. How many feet high is the building? ( the ground is level and both the building and the flagpole are perpendicular to the ground)