Question

What's v75 + v3 ?

Answer 1

do you mean
\[ \sqrt{75} + \sqrt{3} \]?
write 75 as 3*5*5:
\[ \sqrt{5\cdot 5 \cdot 3} + \sqrt{3} \]
notice you have a pair of 5's inside the square root
that means you can simplify that part.