Final answer:
The given equation does not correctly describe the statement that Isaiah is saving $12 per week from his allowance and has $240 after 20 weeks.
Step-by-step explanation:
The given equation is 20 + 12x = 240. To determine if this equation correctly describes the statement that Isaiah is saving $12 per week from his allowance and has $240 after 20 weeks, we can substitute 20 for x and check if the equation holds true.
When we substitute 20 for x in the equation, we get 20 + 12(20) = 20 + 240 = 260, which is not equal to 240. Therefore, the equation does not correctly describe the statement.