The YouTube channel Mind Your Decisions has this puzzle: Solve this to get into Harvard. An admission question from 1869

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I reach the same solution as the video, I just think my way is more elegant. Let’s begin by writing the information like mathematical equations.

(1)	w + c + l = 216
(2)	w + l = 3 * c
(3)	c + l = 1/2 * w

Let’s just look at the first 2 equations.

(1)	w + c + l = 216
(2)	w + 0 + l = 3 * c <=>
	w + c + l = 3 * c + c = 4 * c
(1) & (2)	216 = 4 * c <=>
	216 / 4 = c
	54 = c

Similarly, we can look at the first and last original equations.

(1)	w + c + l = 216
(3)	0 + c + l = 1/2 * w <=>
	w + c + l = 1/2 * w + w = 3/2 * w
(1) & (3)	216 = 3/2 * w <=>
	216 * 2/3 = w
	144 = w

Having come this far, we can plug the values for c and w into the original first equation.

w + c + l = 216 & c = 54 & w = 144 <=>

144 + 54 + l = 216 <=>

l = 216 – 144 – 54 = 18

And we have a solution.