Let me show you how I created a simple web shop icon (shop trolley). In Illustrator (or similar vector software) make a simplified shop trolley “L” shape (the handle + basis).

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Now, we will select the basis line and copy it two more times to get something similar to E shape where the left vertical line end up above the top horizontal line.

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Draw one vertical line that will close the shape.
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As for the wheels, create two circles below the basis of the trolley. Make one ellipse and then a second one, smaller in the middle of the first one.(Do that using Ellipse tool). Select both ellipses, and subtract them with “Pathfinder -> Subtract from shape area” option. There is our wheel 🙂
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Copy that wheel and position them under the basis.
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Now for the background circle follow the same procedure as for the wheels. One small difference is that holding ALT+TAB will make this ellipse a perfect circle. Color it, place it behind the trolley and – voila!

Simple, innit?

Let me know if you need any help.