Math Problems That 8 Year Olds Can Do By Themselves Since 13 is bigger than 10, have your child write the 3 in the answer space and carry the 1 over to the next place value, which is the tens place. Then, add the 1 that was carried to the 1 in the problem for an answer of 2. The final answer is 23 pennies. Third 1. 3 x 12 2. 5 x 9 3. 4 x 1 4.