Explanation:
If the ratio of boys to girls in the class is 2 to 3, this means that for every 2 boys, there are 3 girls.
Let's use the variable "x" to represent the number of boys in the class.
If the ratio of boys to girls is 2 to 3, then the ratio of boys to the total number of students in the class is 2 to 5
We know that there are 18 girls in the class, so the total number of students is:
18 girls + x boys = 18 + x students
And we also know that the ratio of boys to the total number of students is 2 to 5.
So we can set up the following proportion:
2/5 = x/(18 + x)
Cross-multiplying gives:
2(18 + x) = 5x
Expanding the left side gives:
36 + 2x = 5x
Subtracting 2x from both sides gives:
36 = 3x
Dividing both sides by 3 gives:
x = 12
Therefore, there are 12 boys in Mr. Cunningham's class.