There are 24 students in a seventh grade class. They decided to plant birches and roses at the school's backyard. While each girl planted 3 roses, every three boys planted 1 birch. By the end of the day they planted 2424 plants. How many birches were planted?  Choose one
A) 2
B) 5
C) 8
D) 6
E) 4
Let x be the number of roses. Then the number of birches is 24−x, and the number of boys is 3×(24−x). If each girl planted 3 roses, there are x3girls in the class.   We know that there are 24 students in the class. Therefore x3+3(24−x)=24   x+9(24−x)=3⋅24   x+216−9x=72   216−72=8x   1448=x1   x=18   So, students planted 18 roses and 24 - x = 24 - 18= 
<gadget id="calculator">24 - 18</gadget>
<output>6</output>
6 birches.   correct answer is 6)6
<result>D</result>
There are 24 students in a seventh grade class. They decided to plant birches and roses at the school's backyard. While each girl planted 3 roses, every three boys planted 1 birch. By the end of the day they planted 2424 plants. How many birches were planted?