that's an equilateral triangle which means that all sides and angles are equal to each other. So now if you set everything equal to each other you get 2(2x+1)=6x+7y. Now it's just algebra after that, you have to distribute then left side then isolate the variable y and you get a y value. next step is pretty simple just substitute the answer that you got for y into the original equation that included y so you can get an x value. if everything is right it should tell you that the final answer is 14.