what is 10 square root of 3u squared plus 6u squared square root of 3u squared?

Question

i have to add this radical alright thanks

Do you mean [10 sqrt(3u)]^2 + 6u^2*[sqrt(3u)]^2 ?

That would be 100*3u + 6 u^2*3u
= 300 u + 6 u^3

but there are other ways to interpet what you have written. Trying to write out algebraic expressions in words, without using parentheses to clarify the order of operations, leads to confusion and the possibility of different answers.