Step-by-step explanation:
<u>Step 1: Substitute x from the second equation into the second one</u>







<u>Step 2: Substitute y into the second equation</u>




Answer: 
1. 40 units___16 workers
20 units___x= 8 workers
(20*16)/40=8
2. 40 units___16 workers
25 units___x= 10 workers
(25*16)/40=10
3. 40 units___16 workers
100 units___x= 40 workers
(100*16)/40=40
No a sphere consisting of steel at some dimensions such as 3 ft^3 wouldn't weigh the same as a sphere of silicone at 3 ft^3