To multiply these two terms you multiply each individual term in the left parenthesis by each individual term in the right parenthesis.
#(color(red)(sqrt(3)) - color(red)(5sqrt(10)))(color(blue)(5sqrt(10)) - color(blue)(2sqrt(3)))# becomes:
#(color(red)(sqrt(3)) xx color(blue)(5sqrt(10))) - (color(red)(sqrt(3)) xx color(blue)(2sqrt(3))) - (color(red)(5sqrt(10)) xx color(blue)(5sqrt(10))) + (color(red)(5sqrt(10)) xx color(blue)(2sqrt(3)))#
#5sqrt(3)sqrt(10) - 2sqrt(3)sqrt(3) - 25sqrt(10)sqrt(10) + 10sqrt(10)sqrt(3)#
#5sqrt(3 * 10) - (2 * 3) - (25 * 10) + 10sqrt(10 * 3)#
#5sqrt(30) - 6 - 250 + 10sqrt(30)#
We can now group and combine like terms:
#5sqrt(30) + 10sqrt(30) - 6 - 250#
#(5 + 10)sqrt(30) - 256#
#15sqrt(30) - 256#