im pretty sure you got it right with 40!!
This is pretty weird: ax+ b > c is equivalent to ax + b > 0, for instance. c might always be chosen as zero, or b, or any value!
280x <= 348.76, or -280x + 348.76 >= 0,
so a = -280, b = 348.76 and c = 0 is one solution
The answer is 1 3/5.
Hope this helps!
Have a NICE DAY!