Answer:
because the variable is being multiplied by 0.
Step-by-step explanation:
the B in the equation is just a place holder for any number you can think of.
the problem with that is that any number times 0 will always give you 0, so the equation will look like this now
0 = 21
this equation is false because 0 is not equal to 21.
21 is equal to 21.
