How many lights of all colors are on the sign?

Question

On a neon sign, 1/5 of the lights are yellow and the rest are blue and red. There are twice as many blue lights as yellow lights, and there are 200 red lights on the sign. How many lights of all colors are on the sign?

Answer 1

Let B, Y, R be the numbers of blue, yellow and red lights, so there are B+Y+R lights altogether.

Y=(B+Y+R)/5, R=200, B=2Y.

Y=(2Y+Y+200)/5, 5Y=3Y+200, 2Y=200, number of yellow lights, Y=100, so number of blue lights, B=200, and the total number of lights is 500.