Question 1161973
If you reverse the two digits of Emma's age, add 17 and divide by 2, you get Emma's age. How old is she? 
<pre>Let the tens and units digits of her age be T and U
Then we get: {{{matrix(1,3, (10U + T + 17)/2, "=", 10T + U)}}}
10U + T + 17 = 20T + 2U ------ Cross-mutiplying
8U = 19T - 17
{{{matrix(1,3, U, "=", (19T - 17)/8)}}}
I decided to solve for U (units digit) as opposed to T (tens digit) because in most cases, the tens digit is smaller, and I can arrive at the answer much quicker 
Substituting 1 for T results in 0.25 for U, which obviously is NOT an integer
Substituting 2 for T results in 2.625 for U, which obviously is NOT an integer
However, substituting 3 for T results in a value of 5 for U, which obviously is an INTEGER, and so we get {{{highlight_green(matrix(1,5, "Emma's", age, to, be, 35))}}}
I also used Excel and no other digit for T, from 4 - 9, produces an INTEGER-DIGIT for U.