Answer:
Pretend that x and y represents the 2 numbers that we need to find.
According to the information, we know that:
x + y = 21
6x = y
Replace y in the first equation with 6x (because they are equal to each other according to the second equation):
x + y = 21
x + 6x = 21
7x = 21
x = 21/7 = 3
Now have two ways to find y, both will give us the same result:
3 + y = 21 ⇔ y = 21 - 3 = 18
6 · 3 = y ⇔ y = 18
So the numbers that we need to find are 3 and 18.
