The area of a parallelogram is 30 ft and the height is 5 ft. Find the length of the corresponding base.

Hi!

Let's write some equations to solve this.

h = hamburgers
c = cheeseburgers

h + c = 758
h + 58 = c

Let's put the value of c into the first equation. 
h + h + 58 = 758
Simplify
2h + 58 = 758
Subtract 58 from both sides
2h + 58 - 58 = 758 - 58
2h = 700
Divide by 2 on both sides
2h/2 = 700/2
h = 350

350 hamburgers were sold on Sunday

Let's check our answer by putting the value of h into both of our original equations.
350 + c = 758
350 + 58 = c
Solve
350 + 58 = 408
c = 408
350 + 408 = 758

Our answer is correct.

Hope this helps! :)