The correct answer is (a).
A number is divisible by 7 if the remainder when it is divided by 7 is 0. A number that gives 3 as a remainder when divided by 7 is 3 more than a multiple of 7. The first multiple of 7 after 11 is 14, so the first number that gives 3 as a remainder when divided by 7 is 14 + 3 = 17. The last multiple of 7 before 18 is 14, so the last number that gives 3 as a remainder when divided by 7 is 14 – 3 = 11. Therefore, there are 2 such numbers: 17 and 11.
(b) is incorrect because 12 is not divisible by 7.
(c) is incorrect because 15 is divisible by 3, so it cannot give 3 as a remainder when divided by 7.
(d) is incorrect because 18 is divisible by 2, so it cannot give 3 as a remainder when divided by 7.