Katrina is building a deck. She cuts 3 lengths of wood from a 72-inch board. The first length is 30 3/4 inches. The second length is 12 1/4 inches. And the third length is 16 1/4 inches. How much of the original board remains after Katrina makes her cuts?

First add them together

30 and 3/4+12 and 1/4 + 16 and 1/4=30+3/4+12+1/4+16+1/4 = 30+12+16+3/4+1/4+1/4=58+1+1/4=59+1/4=59 and 1/4

subtract from 72

72-59 and 1/4=72 - (59+1/4) = 72-59-1/4=71+1-59-1/4 = 71-59+1-1/4 = 71-59+4/4-1/4=12+3/4

the legnth left is 12 and 3/4 inches