In a question, when it states "a number" without giving a real number, that means it's a variable. Variables are normally letters. In the question, it gives you what letter to use, "y". Start the equation.
The word "decreased" is used when subtracting. In this equation, you are going to be subtracting. Add that to the equation.
"Negative" is used for negative numbers. For example, "negative 1" is going to be -1. In the question, it says "negative 7", which is going to be -7. Add that to the equation.
The phrase "Is the same thing as" means equal. Add that to the equation.
At last, 48. 48 is just 48 as a number. Add that to the equation.
Your answer is: y - (-7) = 48