Make them have common denominators: 14/8(3/3)=42/24, 15/12(2/2)=30/24, 42/24+30/24. Add numerators: 42+30=72, 72/24. Simplify: 72/24=3, 24/24=, 3/1=3. 3 is your answer :)
He isn't right. He needs 1/6 cup of olive oil since 2/3 times 1/4 = 1/6
6.2 you subtract the 0.7 from 6.9 because 0.7 of it is milk chocolate