Question

seven times a two digit number is equal to four times the number obtained by reversing the order of the digits .If the difference of the digits is 3.determine the number

Answer 1

If the number is 'xy'
Y-x=3
7xy=4yx

y=3+x
7(10x+y) =4(10y+x)

70x+7y=40y+4x
3+x=y
70x+7(3+x) =40(3+x) +4x

70x+21+7x=120+40x+4x

77x+21=120+44x

77x-44x=120-21

33x=99
x=3

y=x+3
y=3+3
y=6
Hence The number is 36....