<em><u>The system of linear inequalities are:</u></em>
![a + b \geq 20\\\\2.50a + 7b\leq 80](https://tex.z-dn.net/?f=a%20%2B%20b%20%5Cgeq%2020%5C%5C%5C%5C2.50a%20%2B%207b%5Cleq%2080)
<em><u>Solution:</u></em>
Let "a" be the number of small candles bought
Let "b" be the number of large candles bought
<em><u>He needs to buy at least 20 candles</u></em>
Therefore, number of small candles and number of large candles bought must be at least 20
Thus, we frame a inequality as:
![a + b \geq 20](https://tex.z-dn.net/?f=a%20%2B%20b%20%5Cgeq%2020)
"at least" means greater than or equal to
Here, we used "greater or equal to" symbol because, he can buy 20 candles or more than 20 candles also
From given,
Cost of 1 small candle = $ 2.50
Cost of 1 large candle = $ 7
<em><u>He can spend no more than 80 dollars</u></em>
Which means, he spend maximum 80 dollars or less than 80 dollars also
So we have to use "less than or equal to" symbol
<em><u>Thus, we frame a inequality as:</u></em>
Number of small candles bought x Cost of 1 small candle + number of large candles bought x Cost of 1 large candle
80
![a \times 2.50 + b \times 7 \leq 80\\\\2.50a + 7b\leq 80](https://tex.z-dn.net/?f=a%20%5Ctimes%202.50%20%2B%20b%20%5Ctimes%207%20%5Cleq%2080%5C%5C%5C%5C2.50a%20%2B%207b%5Cleq%2080)
<em><u>Thus the system of linear inequalities are:</u></em>
![a + b \geq 20\\\\2.50a + 7b\leq 80](https://tex.z-dn.net/?f=a%20%2B%20b%20%5Cgeq%2020%5C%5C%5C%5C2.50a%20%2B%207b%5Cleq%2080)