// PL9/twonum3.cpp // Define a class template to hold a pair of numbers (header file) // Niels Walet, Last modified 03/12/2019 #include #include"twonum3.h" using namespace two_num; int main() { int x{1},y{2}; double a{-1.5},b{-2.5}; // Use class template for object representing pair of integers pair_of_numbers ip(x,y); std::cout<<"x+y="<