We need to remember that:
xyz = (x)(y)(z)
if x, y and z are perfect cubes, then xyz would also be a perfect cube
Also,
(x^n)^m = x^(mn)
if it is a perfect cube, then it can be factored into the expression (x^n)^3, wherein n is a whole number.
All should be a perfect cube, given
215x^18(y^3)(z^21)
By writing the terms separately, we would see which one is to be changed.
215 = 5*43, we see this is not a perfect cube, we could changed it to 6^3 or 216
x^18=(x^6)^3
y^3=y^3
z^21=(z^7)^3
The other terms are perfect cubes except for the first one. So the correct answer would be the last option, 215 should be changed.
Answer:
A Exactly one solution
Step-by-step explanation:

Putting y=0 at second equation, we have

The unique solution is 
Yeah sameee, they remove my brainliests too☹️
Answer:
i think it would be a model.
Step-by-step explanation:
Answer:
If
then
and 
a | b | a + b (answer)
0 | 0 | 0
0 | 1 | 1
0 | 2 | 2
1 | 0 | 1
2 | 0 | 2
1 | 1 | 2
2 | 1 | 3
Step-by-step explanation:
Considering the following conditions for the real numbers:

Following the rules of these in-equations, it is possible to deduce:

Then, if the proposed statement is:

The conditions above shall comply the requirements established, but first, analyzing the statement:
If
and
then
,
and
.
If
and b a non negative real number, then
, but because to
, then
. Due to the commutative property of sums, the same behavior will be presented if
and a a non negative real number.
According to that, if
, then
and
.