11.4 Hints

How to get the equations

Number 1:

Relate the prices of the seats.
Relate how much they make for selling all the seats to how much they need to make.
You don't need the total number of seats.

Number 2:

How many points each kind of question is worth=total points
The test has 2 kind of questions for a total of 20 questions

Number 3:

One question is John's order, the other is Serena's order.

Number 4:

The first 2 pictures are equations. Solve them using substitution then figure out the third picture

How to substitute

Solve one of the equations for one variable. The side of this equations are the same, this is always true of equations and is called the Reflexive Property of Equality. Because this variable is the same thing as the other side of the equal sign, you can put the expression in place of the variable.

Turn the variable you solved for in equation 1 to empty parentheses in equation 2. Put the expression that is the same as the variable in those parentheses.

How to solve

The equation you get is just like many that we have solved this year, last year, and in middle school. You use the same old rules. The order of operations, the integer rules, the distributive property, inverse operations, and everything still apply.

I still don't get it

Here's the steps according to PurpleMath
Here's another example
And another

Story to Equations from PurpleMath