You can do math with Vec2, just as you can with plain numbers. It is possible to assign x and y values directly, but you can also do math with the class itself. In this case the operator will be applied to x as well as y:
Vec2 p1(0.1, 0.3);
Vec2 p2(0.3, -0.1);
Vec2 p3 = p1 + p2; // x: 0.4 , y: 0.2
p3 -= 0.1; // x: 0.3 , y: 0.1
5p3 *= 2; // x: 0.6 , y: 0.2
p3 = p1 / 2.f; // x: 0.05, y: 0.15