In the question it is asked how many machines to be added so Isn’t A equals 24 ?
Yes. 32-8 = 24
Blockquote
| Machines = 8 | Time(sec) = 20 | Bolts = 250 |
| Machines = 8 | Time(sec) = 10 | Bolts = 125 |
[ In half the time (10 secs) they will produce half amount of bolts ]
| Machines = 1 | Time(sec) = 10 | Bolts = 125/8 |
The final equation will be (125/8)*X = 500 [X = Number of machines]
You answer should be 32.