First, multiply each term within the parenthesis by the term outside the parenthesis:
#color(red)(sqrt(7))(sqrt(35) + sqrt(7)) =>#
#(color(red)(sqrt(7)) xx sqrt(35)) + (color(red)(sqrt(7)) xx sqrt(7)) =>#
#(color(red)(sqrt(7)) xx sqrt(35)) + 7#
Next, rewrite the term on the left using this rule of radicals:
#sqrt(color(red)(a)) * sqrt(color(blue)(b)) = sqrt(color(red)(a) * color(blue)(b))#
#(color(red)(sqrt(7)) xx color(blue)(sqrt(35))) + 7 =>#
#sqrt(color(red)(7) xx color(blue)(35)) + 7 =>#
#sqrt(color(red)(7) xx color(blue)(7 xx 5)) + 7 =>#
#sqrt(color(red)(49) xx color(blue)(5)) + 7 =>#
#(sqrt(color(red)(49)) xx sqrt(color(blue)(5))) + 7 =>#
#7sqrt(color(blue)(5)) + 7#