text: the radicals must be "the same" before you can add or subtract them! for example you can add 3√2 + 5√2. you treat the radical part like a variable \n3√2 + 5√2= (3+5)√2  =8√2\nto make sure you can add radicals first you must simplify them. lets do your example:\n3√20 + √45 + 2√5\nstep one : simplifying √20 and √45, since √5 is in its simplest form we just leave it like that.\n 3√20 + √45 + 2√5= \n=3√(5x4)+√(9x5)+2√5=\n=3√(5x2^2)+√(3^2x5)+2√5\n\nsince √a^2=a\n    and √(axb)=√a x √b (x means times)\nwe get \n3√5√2^2+√3^2√5+2√5=\n3x2√5+3√5+2√5=\n6√5+3√5+2√5=\n(6+3+2)√5=\n11√5