Puzzle based on balanced equation

Solve this:

Anne buys two melons from the market which are weighed by the seller as shown below: How much did the two pieces of melons weigh together?

Weighing websites

Here are some websites to practice weighing and reading scales. Click on the picture to have a go at home.

Weighing

We've been busy weighing pebbles today!

We measured with different scales, to be really sure.