b+g = 40
4/5 b + 2/3 g = 40-n
2/3 b + 2/3 g = 2/3 * 40
4/5 b + 2/3 g = 40-n
(4/5 - 2/3)b = 40-n - 2/3*40
2/15 b = 40/3 - n
b = 5(40-3n)/2 = 100 - 15n/2
Check: suppose n = 10
b = 25
g = 15
boys who wear: 20
girls who wear: 10
4/5 b + 2/3 g = 40-n
2/3 b + 2/3 g = 2/3 * 40
4/5 b + 2/3 g = 40-n
(4/5 - 2/3)b = 40-n - 2/3*40
2/15 b = 40/3 - n
b = 5(40-3n)/2 = 100 - 15n/2
Check: suppose n = 10
b = 25
g = 15
boys who wear: 20
girls who wear: 10
1. Let's represent the number of boys in the class as b and the number of girls as g.
From the information provided, we know that there are 40 children in total in the class.
So we can write the equation: b + g = 40.
2. We're also given that n children do not wear spectacles, but it doesn't specify if they are boys, girls, or a combination of both.
So, let's assume that n represents the number of boys and girls who do not wear spectacles.
Therefore, the number of children who wear spectacles will be (40 - n).
3. We're told that 4/5 of the boys wear spectacles. This means that out of all the boys (b), 4/5 of them wear spectacles.
So, the number of boys who wear spectacles is (4/5) * b.
4. We're also told that 2/3 of the girls wear spectacles. Similar to above, the number of girls who wear spectacles is (2/3) * g.
5. Now, let's substitute the values from step 3 and 4 into the equation from step 2:
(4/5) * b + (2/3) * g = (40 - n).
By following this process, you can express the number of boys who wear spectacles in terms of n.