SOLUTION: A number consists of two digits whose sum is 10 . If 72 be subtracted from the number , the digits are reversed . Find the number ? Sir can

Let the 1o-digit be x

Let the one-digit be y

Now: x+y=10

y=10-x (subsitution)

Reversed digits: 10y+x

Equation:

10x+y-72=10y+x

Subsitute for y:

10x+(10-x)-72=10(10-x)+x

9x-62=100-9x

18x=162

x=9

y=10-9

y=1

Hence, the to-digit number is 9, and the one digit number is 1 and the whole number is 91.

Paul.