In order to add fractions, you have to have a common denominator. The denominators in these fractions are 3, 2, and 4 (the bottom numbers). To get a common denominator, figure out what number all three of them can go into. Their common factor would be 12 because all three numbers go into 12.
Multiply each numerator in the fraction (the top number) by how much it takes to get from our current denominators (3,2,4) to our final denominator (12).
For example, in 2/3 we know that 3 times 4 equals 12. Multiply the top number by 4 to get 8/12.
In 1/2 we know that 2 times 6 equals 12. Multiply by 6 to get 6/12.
In 1/4 we know that 4 times 3 equals 12. Multiply by 3 to get 3/12.
