Respuesta :

there are 2000 pounds in aton
There are 3 1/2 tons in the truck. 
1 ton = 2,000 pounds

3 tons = 6,000 pounds   1/2 ton = 1,000 pounds
so,
3 tons + 1/2 ton = 6,000 pounds + 1,000 pounds
3 1/2 tons = 7,000 pounds