You reject the Null Hypothesis when you have a small P-Value. Here is an example! Also we never accept the null hypothesis, think of it like this if we bring someone to court you wouldn't say their innocent of a crime, you only know that if they do not get convicted of the crime they are not guilty in the eyes of the law. Same thing applies here, since there could be several answers that satisfy our assumptions made, we can not be certain that 1 of those assumptions is the REAL answer it's just AN answer.
Let the cost of one cup of hot chocolate be = x
Let the cost of one cup of hot tea be = y
Paul paid $ 25.50 for 3 cups of hot chocolate and 4 cups of tea.
Equation becomes = ...(1)
As given, the cost of each cup of tea was 2/3 the cost of each cup of hot chocolate.
.... (2)
Putting the value of y from (2) in (1)
=
=
=
x=4.5
=
y =3
Hence each cup of hot chocolate is $4.50
Each cup of tea is $3.