The temperature of a city is 4°C Next day temperature falls by 5°C Next day temperature = 4-5 = -1°C Hope it helps ...
A standard line equation takes the form of y=mx+b
m= the slope so we see that 2 is next to x in your example
A) Slope = 2
Perpendicular lines will have the negative reciprocal of the original equation's slope
2 -> -
B) 
The ladder would reach 16 feet on the building.
Pythagorean theorem helps find this answer. a^2 +b^2 = c^2