`m=` number of medium pizzas
`l=` number of large pizzas
Since medium pizza costs $5 and large costs $8 you have $40 to spend your equation is
Note that both `m` and `l` must be positive integers.
Possible solutions are `(m,l)=(8,0)` and `(m,l)=(0,5).`
Standard form follows Ax+By=C, whereas A, B, and C are integers while x and y are variables. With that said, using the information you gave, your scenario in standard form would be:
5m+8l=40, where m=# of medium pizzas bought, and l=# of large pizzas bought
To figure out possible combinations, you can plug different numbers into m and then solve for l, or vice versa. You can also graph the equation by plotting out the y-intercept (x=0) and then the x-intercept (y=0), and making a line connecting the two dots, or by rewriting the equation in slope-intercept form and graphing based off of that. In all scenarios, combinations only work if the both variables are whole numbers and non-negative.
those are the possible cominations