Answer:
An equation is expressed or defined by an equals to sign (i.e. =).
Thus,
11 - is an equation.
12 - is an expression.
13 - is an equation.
14 - is an expression.
15 - is an expression.
16 - is an equation.
17 - is an expression.
18 - is an equation.
19 - is an equation.
20 - is an expression