Question

solution of 40-2L/10=54-3k/15

Answer 1

L = k - 70

Answer 2

Is the problem: (40-2L)/10=(54-3k)/15?
If so then the first step is multiply by 10 and 15:
15(40-2L) = 10(54-3k)
Distribute:
600-30L = 540-30k
Subtract 540 from both sides
60-30L = -30k
Divide by 30
2-L = -k
or 2+k = L

Answer 3

You could be correct I took the problem as 40-(2L/10) = (54 - 3k)/15

But I think you are correct TBates.