On May 18, 1980, a massive eruption of Mt. St. Helens in Washington State sent a huge plume of ash more than 50,000 feet into the air. Over the next two weeks, the ash traveled around the world. To move that far, the ash would've had to:. a. reach into the stratosphere. b. dissolve in the nitrogen of the air. c. bind to aerosols in the lithosphere. d. combine with moisture in the troposphere.

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].