9 times a number is that number minus 10
The phrase a number means we define a random/arbitrary variable, let's call it x:
x
9 times a number means we multiply x by 9:
9x
The phrase that number refers back to the original arbitrary variable we defined above, which is x:
x
That number minus 10 means we subtract 10 from x:
x - 10
The word is means equal to, so we set 9x equal to x - 10
9x = x - 10
The phrase a number means we define a random/arbitrary variable, let's call it x:
x
9 times a number means we multiply x by 9:
9x
The phrase that number refers back to the original arbitrary variable we defined above, which is x:
x
That number minus 10 means we subtract 10 from x:
x - 10
The word is means equal to, so we set 9x equal to x - 10
9x = x - 10