how many positive even integers less than 100 contain digits 7 or 9 ?
"two digit numbers : 7 at tens place : 70 , 72,74 , 76,78 9 at tens place : 90 , 92,94 , 96,98 if 7 and 9 is at units place , the number cant be even total : 5 + 5 = 10 answer e"
multiply(7, const_2)