Attached is how I would have made the part.
R17 and R3 means those features have a radius of 17 and 3 units, respectively.
It's the radius. Fillet or Arc.
I'm sorry being a Solidworks beginner but,
where the arc(R=17) starts from ? the the small circle center?
In this example, it looks as if the hole and the arc share the same center point. If I were going to model this part, I would model the body first, then add the holes, and finally the fillets.
this sketch seems hard
any ideas how to start with it from front?
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