Aplastic 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