Dylan has two cubes of iron. the larger cube has twice the mass of the smaller cube. he measures the smaller cube. it's mass is 20 grams, and its density is 7.87 g/cm3. what's the larger cube's volume?

Density
is given by
where m is the mass of the object
V is the Volume of the object

let m1 be the mass of the smaller cube
let m2 be the mass of the larger cube

you know that the larger cube has twice the mass of the smaller cube
or m2=2*m1

so apply this information into the density equation and you can determine the volume of the larger cube