Find the sum or difference. Write your answer in simplest form

3/8 + 1/4​

What is the value of x in the diagram below?

What is the volume of a cone with a height of 6 cm in the radius of 2 cm

He mass of a single atom of carbon can be found by dividing the atomic mass (12.01 g) by 6.022 x 10^23. which is the mass of a single carbon atom, correctly written in scientific notation with the correct number of significant figures?