Sorry, I couldn't figure out the last one, it just takes a lot of trial and error and luck :(
You know that S times A is the digit N. Then, A squared plus whatever the first digit of the2 digit number XN is MA.
A cannot be five because if you were to do 5 times 5 it would be 25. A squared is 25 and the last digit is already A so added on to anything else the equation would be false. So the only considerable value for S would be one, but then A times S would be 5, but N is not A. I hope you get what I mean.
A cannot be 6 for the same reason (just change the 5 to six on my last pragraph).
If A were 7 then you'd have to find something to add to 49 to make it end in 7, which means adding 6. 7 times 9 is 63, so S could be 9. 79 times 7 is 573. That is the answer. A = 7, S = 9, M = 5, N = 3.
As for NINE - FOUR = FIVE, E - R is E so R must be 0.The only one digit number a number can be subtracted by to get itself is 0.
Now, N - U = V, or 1N - U = V
Let's say N is 3 and U is 6. V would be 7.
We've just took one from I. I - 1 - O = I. 1+O must be 10 or 0, but O must be positive, so O = 9. Let's say I is 5.
We just borrowed one form N. N-1 - F = F. N - 1 = 2 times F.
But we know that N is 3. 2 = 2 times F. F is 1.
Let's just make E = 8
My final answer is 3538 - 1960 = 1578
There are MANY other answers though.
N = 3, I = 5, E = 8, O = 9, U = 6, R = 0, V = 7.
