Let the number be xy ,
xy = 10x + y. when reversed = yx = 10y + x
x = 2y ........(a)
10x + y + 10y + x = 66.........(b)
10(2y) + y + 10y + 2y = 66
20y + y + 10y + 2y = 66
33y = 66
y = 66/33
y = 2
x = 2y = 2*2 = 4
Recall the original number is xy = 42.