194916

Question 1

Answer:
a=4
b=2
c=8
d=5
e=7

so 142857 x 3 = 428571

I started with the single units and worked out which multiple of 3 ended in a 1, which was 3x7=21. I then substituted the letter e in the answer for 7, deducted the 2 that I had carried over from 21 and then worked out which multiple of 3 ended in 5, which was 3x5=15, so d=5. I then repeated this process, substituting d in the answer for 5, deducting the 1 I had carried over and then worked out which multiple of 3 ended in 4, which was 3x8=24. I then repeated this to work out all the other letters.

Question 2

Answers:
f=8
g=5
h=7
i=1
j=4

so 285714 x 3 = 857142