To solve these linear programming problems using graphical and simplex methods, I'll outline the approach for each one.

Problem 1

Maximize $Z = 3X_1 + 3X_2$ subject to:

1. $2X_1 + X_2 \leq 10$
2. $3X_1 + 4X_2 \geq 72$
3. $X_1 \geq 0, X_2 \geq 0$

Problem 2

Maximize $Z = 3X_1 + X_2$ subject to:

1. $2X_1 - X_2 \leq 10$
2. $X_1 \leq 20$
3. $X_1 \geq 0, X_2 \geq 0$

Problem 3

Maximize $Z = 5X_1 - 2X_2$ subject to:

1. $2X_1 - X_2 \leq 10$
2. $X_1 \leq 20$
3. $X_1 \geq 0, X_2 \geq 0$

Problem 4

Maximize $Z = 6X_1 + 12X_2$ subject to:

1. $X_1 + 2X_2 \leq 50$
2. $2X_1 + X_2 \leq 40$
3. $X_1 \geq 0, X_2 \geq 0$

Problem 5

Maximize $Z = 2X_1 + 3X_2$ subject to:

1. $4X_1 + 5X_2 \leq 100$
2. $2X_1 + 4X_2 \leq 80$
3. $X_1 \geq 0, X_2 \geq 0$

To solve each problem using the graphical method:

1. Graph each constraint by converting inequalities to equations.
2. Determine the feasible region by identifying where all constraints intersect and satisfy all inequalities.
3. Locate the vertices of the feasible region.
4. Evaluate $Z$ at each vertex to find the maximum value.

To solve each problem using the simplex method:

1. Set up the initial simplex tableau based on the objective function and constraints.
2. Identify the pivot column and row to determine the entering and exiting variables.
3. Perform row operations to update the tableau.
4. Continue iterating until an optimal solution is reached where no further positive entries are in the objective row for a maximization problem.

Would you like me to solve one of these problems step-by-step using either the graphical or simplex method?

Here are 5 follow-up questions to enhance understanding:

1. How is the feasible region determined in a graphical method solution?
2. What role does the pivot element play in the simplex method?
3. How do you determine which variable should enter or leave the basis in the simplex method?
4. Why are constraints like $X_1 \geq 0$ and $X_2 \geq 0$ essential in linear programming?
5. How does changing the coefficients in the objective function affect the optimal solution?

Tip: Always check each vertex of the feasible region when using the graphical method, as the optimal solution must lie on one of these vertices.