You must ensure your fractions have common denominators. For this equation you must convert 2/3 into something over 6, so you will multiply 2/3 by 2 and end up with 4/6.
7-4=3, and 1/6-4/6=-3/6
3(18/6)-3/6=2.5(15/6) or if you have paper and pencil just subtract normally.
