Well, you're given that

. I think the extra information is extraneous, unless there's something more that you forgot to add.
Hope I could be of some assistance. :)
Answer:
4.73205080757
Step-by-step explanation:
<span>2<span>(<span>y−<span>3<span>(<span>y−5</span>)</span></span></span>)</span></span><span>=<span><span>(2)</span><span>(<span>y+<span><span>−<span>3y</span></span>+15</span></span>)</span></span></span><span>=<span><span><span>(2)</span><span>(y)</span></span>+<span><span>(2)</span><span>(<span><span>−<span>3y</span></span>+15</span>)</span></span></span></span><span>=<span><span><span>2y</span>−<span>6y</span></span>+30</span></span><span>=<span><span>−<span>4y</span></span>+<span>30</span></span></span>