



 
Hi Maria, Since the number is even its units digit must be even, that is 0, 2, 4, 6, or 8. Suppose the units digit is 8 then the sum of the other two digits is $15  8 = 7.$ Find two digits which have a sum of $7.$ That gives you a number that could be Sue's favourite. Find another two digits which have a sum of $7.$ Remember that if the sum of two digits is $7$ you can switch their order and the sum is still $7.$ Watch out that your son doesn't make the hundreds digit of Sues favourite digit a $0,$ because then it is really a two digit number. Once you have found some possibilities consider numbers where the units digit is $6.$ In this case what is the sum of the other two digits? I hope this helps,  


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