To determine how many there are in total/separate, we need to know how many pounds are in 1 ton.
1 ton = 2,000 pounds.
Since we have 3, 5 and 7 tons, let's convert them.
3(2,000) = 6,000
5(2,000) = 10,000
7(2,000) = 14,000
We have either 6,000 / 10,000 / 14,000 pounds as translations, or you maybe want the sum.
To find the sum, we add all the numbers together.
6,000 + 10,000 = 16,000
16,000 + 14,000 = 30,000
Your answer is 30,000 pounds.
I hope this helps!