Which number in the monomial 215x18y3z21 needs to be changed to make it a perfect cube?

3

18

21

215

Remember

xyz = (x) (y) (z)

if x and y and z are all perfect cubes, xyz is also a perfect cube

remmeber

(x^n) ^m=x^ (mn)

so if it is perfect cube it can be factored into

(x^n) ^3, such taht n is a whole number

basiclaly, see if the expoent is divisble by 3

all of them should be perfect cubes

215x^18y^3z^21

split them up to see which ones need changing

215=5*43, not a perfect cube

could be changed to 6^3, which is 216

x^18 = (x^6) ^3

y^3=y^3

z^21 = (z^7) ^3

the 215 needs to be changed