find the 18 th term of an arithmetic progression whose first term is 4 and the common difference is 5 .
"n th term of a . p = a + ( n - 1 ) * d = 4 + ( 18 - 1 ) * 4 , = 4 + 68 = 72 . answer : c"
add(multiply(subtract(18, const_1), 5), 4)