(a) there are 8C2 = 28 ways of picking 2 girls from 8
And there are 21C4 = 5985 ways of picking 4 boys
Required number of ways for 2g / 4b = 28 * 5985 = 167,580
(b) at least 2 girls means combinations of 2g/4b , 3g,3b , 4g/2b , 5g 1b or
6 girls.
2g/4b = 167,580 ways
3g/3b = 8C3 * 21C3 = 56 * 1330 = 74,480
4g/2b = 8C4* 21C2 = 70 * 210 = 14,700
5g 1b = 8C5* 21 = 56*21 = 1176
6 girls = 8C6 = 28
adding these up we get the answer to (b) which is 257,964
See the blue dot in the attached image.
First, find the x value on the coordinate plane. The x value is the first number in the point coordinates, so in this case, it is 4. Move to the right 4. (If it was negative, you would move to the left.)
Then, find the y value, which is the second number of the coordinates. In this case, it is -1, so move down 1. (If it was positive, you’d move up.)
Now, mark this point. This is (4, -1).