The first step to solving this is writing an equation to put it in numbers rather than words.
When a number is unknown, it is represented by a variable, usually x. But of course, the letter you use doesn't matter.
The question says that an unknown number plus 9 times 6 is equal to 7 times that number minus 4.
That means:
(x + 9) • 6 = 7x - 4
Note that the unknown and 9 are in parenthesis. This is because it says the sum of them are being multiplied.
Before you can solve, you must simplify.
Using the distributive property, multiply 6 by each term in the parentheses.
6 • x = 6x
6 • 9 = 54
This leaves us with 6x + 54 = 7x - 4.
Now you need to isolate the variable on one side and a known number on the other.
To keep it simple, let's subtract 6x from both sides.
7x - 6x = 1x = x
This gets us to 54 = x - 4
Now just add 4 to both sides to isolate the variable.
54 + 4 = 58
This means x = 58.
Now just check your work!
(58 + 9) • 6 = 7(58) - 4
58 + 9 = 67
67 • 6 = 402
Now the other side:
7 • 58 = 406
406 - 4 = 402
So the final answer is x, or just the unknown number in general, is 58.