Question

Define a variable and write an expression for the phrase

the quotient of 2 times a number and 19

Answer 1

2x / 19 is the answer

Answer 2

Let the number of apples in a bag be x apples. Basically its assigning a letter (variable) to an unknown quantity.
The phrase in the question can be written as
2x / 19 where x is a variable. 2x means '2 times x'.