How to model a reducing wye pipe joint in solidworks?

It is ugly, but based on the information provided in the drawing, it is as good as it can be.
SW file is 2017. Step also attached.

You could browse the library for some, and see how they are made.

Or you could download the model below, it is for the attached image. You could then go into it and adjust the settings to fit your needs.

I would start by extruding the tubes at their respective OD's and on their respective planes. Then go through and clean it up.

I am not sure if you are looking for this. I have never worked with Wye Pipe joint before. But I made a rough version. You can check it here.

I THINK THIS IS THE BEST SOLUTION FOR THIS SHEET METAL FORMED PART ON A SHEET ROLLER BENDER.