Answer:
, x = 6 ton
Explanation:
The truck can be filled with a total of 20 ton.
There are already 14 ton inside the truck, so if we call x the weight of goods that we can still add into the truck, we know that (x+14) must be equal at most at 20. Therefore, the inequality becomes:

Solving it, we find

which means that the most amount of goods that could be added to the truck is 6 tons.