Question

Owen has 20% more marbles than Danny. Danny has 40% less marbles than Connie. Owen has 21 marbles less than Connie. How many marbles does Danny have?

Answer 1

o = 1.2d
d = 0.6c
o = c-21

c-21 = 1.2(0.6c)
c = 75

d = .6c = 45

Answer 2

Please explain O = 1.2d

Answer 3

Steve, could you please explain how you got c = 75

Answer 4

The o,c,d stand for Owen, Danny, Connie.

We are told that Owen has 20% more than Danny, so o=1.2d (d + .2*d)

Now, just start substituting...

o = 1.2d
o = c-21
So,

c-21 = 1.2d

But, we also know that d = 0.6c, so

c-21 = 1.2(0.6c)
c-21 = .72c
.28c = 21
c = 75

Answer 5

actually, we don't really need to know what c is. We could have substituted the other way, but the arithmetic gets a bit messier:

c-21 = 1.2d
(d/.6)-21 = 1.2d
d(1/.6 - 1.2) = 21
d(1-.72)/.6 = 21
.28d = 12.6
d = 45