Answer:
m = 300
Step-by-step explanation:

multiply both sides of the equation by 5

Incorrect.
Go through the numbers and you'll find un-prime numbers ending in 1:
21, 81, 121,...
D=y2-y1
D+y1= y2-y1+y1 add y1 to both sides to cancel it out.
D+y1=y2 that drops -y1 for the right side but the left remains.
And that's your answer.
Cheeseburgers = 274
Hamburgers = 325
Divide 599 by 2 = 299.50 total burgers split in half
Divide 51 by 2= 25.50
Subtract 299.50- 25.50= 274cheeseburgers
Add 299.50+ 25.50= 325hamburgers