So first we need to make all of the denominators the same. To do this we multiply the top and bottom of the fraction. Multiply the top and bottom of 1/2 to get 4/8. then multiply the top and bottom of 3/4 by 2 to get 6/8. then add the numerators: 4+6+7= 17. Your answer is 17/8.
Keep in mind that we are not changing the quantity of the fractions, we are just changing how the whole is divided. Hope this helps (let me know if I confused you and I'll elaborate with a chart)