Can someone plz help me with this one problem this is my last question!

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?

How many 3-digit numbers can you write using only digits 1 and 7? (of course, digits can repeat.) how many 3-digit numbers can you write using only digits 1 and 7? (of course, digits can repeat.)

Which of the following values in the set below will make the equation 5x + 6 = 6 true? (only input the number.) {0, 1, 2, 3, 4}