Find the rate in which both balls make one full rotation around the track.
Ball A:

It takes 30 seconds for Ball A to make a full rotation.
Ball B:

It takes 20 seconds for Ball B to make a full rotation.
Find the least common multiple of 20 and 30 to find the time at which they'll meet.
Multiples of 20: {20,40,60}
Multiples of 30: {30,60}
60 is the least common multiple of both 20 and 30.
The balls will meet again at
60 seconds.
If you speak a different language this person can interpret your speaking into the language understandable by the other party
252 is the answer for your question
Answer:
x/2 + 21 = 36
First we get rid of constants to isolate the variable.
In order to do that we must do the inverse operation.
Inverse operation of addition is subtraction.
-21 -21(subtracting 21 from both sides, whatever we do to the left side we do it to the right side too)
x/2 = 15
inverse property of division is multiplication
x2 x2
X = 30
The answer is 3
because 18/27 = 2/3