Let the unknown number be x.
Negative 48 decreased by a number: -48 - x
Is the same as the sum of 4 times a number and 7:
-48 - x = 4x + 7
Let's find the number:
-48x - x = 4x + 7
-48x = 4x + 7
Subtract 4x from both sides:
-48x - 4x = 4x - 4x + 7
-52x = 7
