Here you want to find a common denominator. 12 is a good one. so you need to find out what the fractions will be if the denominator is 12. How to do: 2*4=8 3*4=12 2/3=8/12
1*3=3 4*3=12 1/4=3/12
Now add those to see how many girls have brown or blue eyes. 8/12+3/12=11/12 Now do a whole minus 11/12. 12/12-12/12=1/12 So.... 1/12 of the girls do not have brown or blue eyes.