Let the unit digit be x. Ten’s digit = y ⇒ Original number = 10 y + x New number when digits are reversed = 10x + y According to the statement, 10y+x+18=10x+y 9y=18=9x y+2=x 2=x−y Let x=3 and y=1 Prime number 13, 31. When x=9,y=7. Prime numbers are 79, 97. There are two possible numbers.