First, we can use this rule of radicals to simplify two of the terms:
#sqrt(a * b) = sqrt(a) * sqrt(b)#
#-color(red)(sqrt(45)) + 2sqrt(5) - color(red)(sqrt(20)) - 2sqrt(6) =>#
#-color(red)(sqrt(9 * 5)) + 2sqrt(5) - color(red)(sqrt(4 * 5)) - 2sqrt(6) =>#
#-(color(red)(sqrt(9)) * color(red)(sqrt(5))) + 2sqrt(5) - (color(red)(sqrt(4)) * color(red)(sqrt(5))) - 2sqrt(6) =>#
#-(3color(red)(sqrt(5))) + 2sqrt(5) - (2color(red)(sqrt(5))) - 2sqrt(6) =>#
#-3sqrt(5) + 2sqrt(5) - 2sqrt(5) - 2sqrt(6)#
We can now combine like terms:
#-3sqrt(5) + (2 - 2)sqrt(5) - 2sqrt(6) =>#
#-3sqrt(5) + (0 * sqrt(5)) - 2sqrt(6) =>#
#-3sqrt(5) - 2sqrt(6) =>#