To start, let's write the inequality that represents the situation. Elliot needs at least $218 to buy the bike, and he has already earned $40. He will earn $20 for each lawn he mows.
We can set up the inequality based on his earnings:
\[ 20x + 40 \geq 218 \]
Here, \( x \) represents the number of lawns he mows.
Now, we'll solve the inequality to find the minimum number of lawns he needs to mow.
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Subtract 40 from both sides:
\[ 20x \geq 218 - 40 \] \[ 20x \geq 178 \]
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Divide both sides by 20:
\[ x \geq \frac{178}{20} \] \[ x \geq 8.9 \]
Since \( x \) represents the number of lawns and must be a whole number, we round up to the nearest whole number:
\[ x \geq 9 \]
So, Elliot needs to mow a minimum of 9 lawns to buy the new BMX bike.
To summarize:
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The inequality he can use is:
\( 20x + 40 \geq 218 \) -
The solution to the inequality shows that he must mow at least 9 lawns.