Mr.Green will buy pencils and pens for his students for the school year.
He can spend no more than $30 on the pencils and pens.
Pencils cost $0.15 each, and pens cost $0.75 each.
He needs to bug at least 3 times as many pencils as pens
Let's say Mr. Green buys x pens. Since he needs to buy at least 3 times as many pencils as pens, he needs to buy at least 3x pencils.
The cost of the pens is 0.75x.
The cost of the pencils is 0.15(3x) = 0.45x.
He can spend no more than $30, so:
0.75x + 0.45x ≤ 30
1.2x ≤ 30
x ≤ 30/1.2
x ≤ 25
Therefore, Mr. Green can buy a maximum of 25 pens.
Since he needs to buy at least 3 times as many pencils as pens, he needs to buy at least 3*25 = 75 pencils.
Therefore, Mr. Green can buy a maximum of 75 pencils.