True or false ? the first great civilization all had one thing in common: access to a river or other natural water source that allowed them to grow surplus amount of food

This is true; one must have water in order to grow crops, without a source of water you cannot grow a surplus amount of food. Rivers such as the Nile in modern-day Egypt and the Ganges in modern-day India were water sources that the first great civilizations relied on.

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].