The appalachian mountains were formed about 480 million years ago. two processes have form the mountains we see today. what are they? a) faulting built the mountains and erosion wore them down. b) volcanoes built the mountains and erosion wore them down. c) volcanoes built the mountains and earthquakes tore them down. d) earthquakes built the mountains and weathering wore them down.

Amath expression is a collection of one or more terms, which are separated by the signs ( + , - , x , / ).example :   8+b8+b  or  a−3a−3in algebra, an equation is a mathematical statement with two expressions where, each expression is separated by an equal (=) sign. variables can be present on both the sides of the equality (=) sign and we use letters to denote such variables.example 1:   x=4+2x=4+2  , [here, we can observe that the variable is present only on one side of the equation].example 2:   2x+3=x+42x+3=x+4  , [here, we can observe that the variables are present on both side of the equation].