1. Puzzle A
Puzzle B

2. The difference between my digits is 4
I am a 2-digit number
The difference between my digits is 4
I am a multiple of 7
What am I?
Answer: 84

3. Insert + – x or ÷ each time you see
Insert + – x or ÷ each time you see ?, so the results of both the 4-number and 7-number calculations are 12 when working one step at a time from left to right (and no brackets allowed):
2 ? 4 ? 6 ? 8 = 12
1 ? 2 ? 3 ? 4 ? 5 ? 6 ? 7 = 12
Answer:
first one : =12
second one: 1+2*3-4*5-6-7=12 OR =12
There are other possible solutions too.