y*y^5*y^5

y is the same thing as y¹

Now we have:

y¹*y⁵*y⁵

Now we have to remember that if we multiply numbers with exponets, and they have the same base, we can add the exponets. (y would be the same base here)

 y¹*y⁵*y⁵

 y^(1+5+5)

y¹¹

 

So this expression simplifes to y¹¹.