20x+580=30x+ 100

x=48

48x20+580= 1540 copies

2, solution, the unit number is x, then the ten digits are 3x.

30x+x+ 10x+3x=88

x=2 2x3=6

The original two-digit number was 62.

3. After driving X kilometers, there is still 12-0.5x left.

When x=5, 12-0.5x5=9.5 liters, leaving 9.5 liters.

When x= 13, 12-0.5x 13=5.5 liters, leaving 5.5 liters.

12 divided by 0.5=24 kilometers, you have to refuel if you drive 24 kilometers at most.