This involves setting up a system of linear equations.
Using the info given in the problem, Betty's purchase can be expressed by:
2h + d = 11
In addition, Jose's purchase can be expressed as:
2h + 3d = 17
We now have a system of two equations with two unknowns, which can be solved by using either the Substitution Method or the Elimination Method. Let's use the Substitution Method by solving the first equation for d.
2h + d = 11
d = 11 - 2h
Now, we can replace every instance of d in the second equation with the expression (11 - 2h)
2h + 3(11 - 2h) = 17
We now have an equation in terms of one variable, which we can easily solve. You should be able to handle the rest, Cynthia, in order to determine the price of a hot dog and the price of a soda.