Please help!!! pick ab or c. d is wrong!

Plz hurry evaluate the expression a+b where a=8 and b=19

Intro biblioteca sunt 462 de carti cu 198 mai putine enciclipedii si cu 47 mai multe dictionare decat enciclopedii cate enciclopedii sunt in biblioteca

The distribution of a sample of the outside diameters of pvc pipes approximates a symmetrical, bell-shaped distribution. the arithmetic mean is 14.0 inches, and the standard deviation is 0.1 inches. about 68% of the outside diameters lie between what two amounts?