Use a proportion to find what number is 40% of 10y
so far i have
x/10y=40/100

I believe that what you would have to do is find 40% of 10 and then add the y. I got the answer 4y, but I'm not sure if that's what your looking for. Sorry if this isn't, hope I did help, even if it was a little :) 

Byou start by adding them all and setting them equal to 180 since that is half of the total degrees in a circle.(2x+8) + (3x-14) + (3x-14) = 1808x-20 = 1808x = 200x = 25

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