5x-y=-1 + -5x+3y=25 this is elimination two variable

A20? -foot ladder is placed against a vertical wall of a? building, with the bottom of the ladder standing on level ground 19 feet from the base of the building. how high up the wall does the ladder? reach?

Determine which postulate or theorem can be used to prove that lmn =nmo

Idon't get undoing if its pass adding and subtracting so can someone ? x-2 over 5 = 18