the word "difference" implies subtraction. The "and" separates the two quantities under consideration. The word "times" indicates multiplication.
So, another way to write the same thing is "multiply 7 and y, then subtract 1"
7y - 1
One thing I always recommend is that you make a "Math - English Dictionary" that has the math symbol, examples of how it is used, and all the words in English that mean use the operation.