Use the equation y=mx+b where m is the slope (how much it increases each time) and b is the y intercept (starting point).
Your equation would be: y=12x+0 because they eat 12 pounds each day and they start out having eaten 0 pounds.
To solve the equation, plug in the total amount of food for y and use algebra to solve for x:
250=12x
(divide by 12)
(250/12)=x
X=20.833
Their food would last approximately 20 days. (Make sure you round if required)
