12√18-6√20-3√50-8√45
*Break each radical up into the product of a radical of a perfect square and a second radical*
12(√9*√2)-6(√4*√5)-3(√25*√2)-8(√9*√5)
*Simplify the radicals*
12(3√2)-6(2√5)-3(5√2)-8(3√5)
*Distribute*
36√2-12√5-15√2-24√5
*Combine like terms*
21√2-36√5
Hope this helps!!
