A plastic bin contains red, yellow, and green key chains. Out of 350 key chains, 10% percent are yellow. Of the remaining key chains, 3/5 are green. How many red key chains are inside the bin?

There are 350 key chains,

10% are yellow, the number of yellow is 350 x10 / 100 = 35

the number of green, 3/5

let's find 3/5 of 350, it is 3/5x 350 = 210

there are 210 green

and 210 green represents 210*100/350=60%

so the percentage of the red is

100%=60%+10%+X, where X is the percentage of the red key

so X = 100%-70%=30%

and the number of red key is 350x30 / 100=105