How I solved the Challenge question2 : 4?2 X 74 = 33458
Going by the digit sums above equation can be written as –> ? X 2 = 4
so digit sum of the first number has to be 2 for the above equation to be true. Digit sum of the first number with already given numbers there is 6. If a 5 can be added, digit sum of it would become 11 thats equal to 2. So the smuged number in the first figure is 5.
452 X 74 = 33458
Still trying to understand Challenge question1.