#f(x)# is a rational function and as such it is continuous for every #x# in its domain. As the function is defined for #x=7# so, by definition of continuity, its limit equals its value:
#lim_(x->7) (5x)/sqrt(x+2) = [(5x)/sqrt(x+2)]_(x=7) = (5*7)/sqrt(7+2) =35/sqrt(9) =35/3#